Merge branch 'js/t6026-clean-up'

[alt-git.git] / diff.c

/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include "cache.h"
#include "tempfile.h"
#include "quote.h"
#include "diff.h"
#include "diffcore.h"
#include "delta.h"
#include "xdiff-interface.h"
#include "color.h"
#include "attr.h"
#include "run-command.h"
#include "utf8.h"
#include "userdiff.h"
#include "submodule-config.h"
#include "submodule.h"
#include "ll-merge.h"
#include "string-list.h"
#include "argv-array.h"
#include "graph.h"

#ifdef NO_FAST_WORKING_DIRECTORY
#define FAST_WORKING_DIRECTORY 0
#else
#define FAST_WORKING_DIRECTORY 1
#endif

static int diff_detect_rename_default;
static int diff_compaction_heuristic; /* experimental */
static int diff_rename_limit_default = 400;
static int diff_suppress_blank_empty;
static int diff_use_color_default = -1;
static int diff_context_default = 3;
static const char *diff_word_regex_cfg;
static const char *external_diff_cmd_cfg;
static const char *diff_order_file_cfg;
int diff_auto_refresh_index = 1;
static int diff_mnemonic_prefix;
static int diff_no_prefix;
static int diff_stat_graph_width;
static int diff_dirstat_permille_default = 30;
static struct diff_options default_diff_options;
static long diff_algorithm;

static char diff_colors[][COLOR_MAXLEN] = {
        GIT_COLOR_RESET,
        GIT_COLOR_NORMAL,       /* CONTEXT */
        GIT_COLOR_BOLD,         /* METAINFO */
        GIT_COLOR_CYAN,         /* FRAGINFO */
        GIT_COLOR_RED,          /* OLD */
        GIT_COLOR_GREEN,        /* NEW */
        GIT_COLOR_YELLOW,       /* COMMIT */
        GIT_COLOR_BG_RED,       /* WHITESPACE */
        GIT_COLOR_NORMAL,       /* FUNCINFO */
};

static int parse_diff_color_slot(const char *var)
{
        if (!strcasecmp(var, "context") || !strcasecmp(var, "plain"))
                return DIFF_CONTEXT;
        if (!strcasecmp(var, "meta"))
                return DIFF_METAINFO;
        if (!strcasecmp(var, "frag"))
                return DIFF_FRAGINFO;
        if (!strcasecmp(var, "old"))
                return DIFF_FILE_OLD;
        if (!strcasecmp(var, "new"))
                return DIFF_FILE_NEW;
        if (!strcasecmp(var, "commit"))
                return DIFF_COMMIT;
        if (!strcasecmp(var, "whitespace"))
                return DIFF_WHITESPACE;
        if (!strcasecmp(var, "func"))
                return DIFF_FUNCINFO;
        return -1;
}

static int parse_dirstat_params(struct diff_options *options, const char *params_string,
                                struct strbuf *errmsg)
{
        char *params_copy = xstrdup(params_string);
        struct string_list params = STRING_LIST_INIT_NODUP;
        int ret = 0;
        int i;

        if (*params_copy)
                string_list_split_in_place(&params, params_copy, ',', -1);
        for (i = 0; i < params.nr; i++) {
                const char *p = params.items[i].string;
                if (!strcmp(p, "changes")) {
                        DIFF_OPT_CLR(options, DIRSTAT_BY_LINE);
                        DIFF_OPT_CLR(options, DIRSTAT_BY_FILE);
                } else if (!strcmp(p, "lines")) {
                        DIFF_OPT_SET(options, DIRSTAT_BY_LINE);
                        DIFF_OPT_CLR(options, DIRSTAT_BY_FILE);
                } else if (!strcmp(p, "files")) {
                        DIFF_OPT_CLR(options, DIRSTAT_BY_LINE);
                        DIFF_OPT_SET(options, DIRSTAT_BY_FILE);
                } else if (!strcmp(p, "noncumulative")) {
                        DIFF_OPT_CLR(options, DIRSTAT_CUMULATIVE);
                } else if (!strcmp(p, "cumulative")) {
                        DIFF_OPT_SET(options, DIRSTAT_CUMULATIVE);
                } else if (isdigit(*p)) {
                        char *end;
                        int permille = strtoul(p, &end, 10) * 10;
                        if (*end == '.' && isdigit(*++end)) {
                                /* only use first digit */
                                permille += *end - '0';
                                /* .. and ignore any further digits */
                                while (isdigit(*++end))
                                        ; /* nothing */
                        }
                        if (!*end)
                                options->dirstat_permille = permille;
                        else {
                                strbuf_addf(errmsg, _("  Failed to parse dirstat cut-off percentage '%s'\n"),
                                            p);
                                ret++;
                        }
                } else {
                        strbuf_addf(errmsg, _("  Unknown dirstat parameter '%s'\n"), p);
                        ret++;
                }

        }
        string_list_clear(&params, 0);
        free(params_copy);
        return ret;
}

static int parse_submodule_params(struct diff_options *options, const char *value)
{
        if (!strcmp(value, "log"))
                options->submodule_format = DIFF_SUBMODULE_LOG;
        else if (!strcmp(value, "short"))
                options->submodule_format = DIFF_SUBMODULE_SHORT;
        else if (!strcmp(value, "diff"))
                options->submodule_format = DIFF_SUBMODULE_INLINE_DIFF;
        else
                return -1;
        return 0;
}

static int git_config_rename(const char *var, const char *value)
{
        if (!value)
                return DIFF_DETECT_RENAME;
        if (!strcasecmp(value, "copies") || !strcasecmp(value, "copy"))
                return  DIFF_DETECT_COPY;
        return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
}

long parse_algorithm_value(const char *value)
{
        if (!value)
                return -1;
        else if (!strcasecmp(value, "myers") || !strcasecmp(value, "default"))
                return 0;
        else if (!strcasecmp(value, "minimal"))
                return XDF_NEED_MINIMAL;
        else if (!strcasecmp(value, "patience"))
                return XDF_PATIENCE_DIFF;
        else if (!strcasecmp(value, "histogram"))
                return XDF_HISTOGRAM_DIFF;
        return -1;
}

/*
 * These are to give UI layer defaults.
 * The core-level commands such as git-diff-files should
 * never be affected by the setting of diff.renames
 * the user happens to have in the configuration file.
 */
void init_diff_ui_defaults(void)
{
        diff_detect_rename_default = 1;
}

int git_diff_ui_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
                diff_use_color_default = git_config_colorbool(var, value);
                return 0;
        }
        if (!strcmp(var, "diff.context")) {
                diff_context_default = git_config_int(var, value);
                if (diff_context_default < 0)
                        return -1;
                return 0;
        }
        if (!strcmp(var, "diff.renames")) {
                diff_detect_rename_default = git_config_rename(var, value);
                return 0;
        }
        if (!strcmp(var, "diff.compactionheuristic")) {
                diff_compaction_heuristic = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "diff.autorefreshindex")) {
                diff_auto_refresh_index = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "diff.mnemonicprefix")) {
                diff_mnemonic_prefix = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "diff.noprefix")) {
                diff_no_prefix = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "diff.statgraphwidth")) {
                diff_stat_graph_width = git_config_int(var, value);
                return 0;
        }
        if (!strcmp(var, "diff.external"))
                return git_config_string(&external_diff_cmd_cfg, var, value);
        if (!strcmp(var, "diff.wordregex"))
                return git_config_string(&diff_word_regex_cfg, var, value);
        if (!strcmp(var, "diff.orderfile"))
                return git_config_pathname(&diff_order_file_cfg, var, value);

        if (!strcmp(var, "diff.ignoresubmodules"))
                handle_ignore_submodules_arg(&default_diff_options, value);

        if (!strcmp(var, "diff.submodule")) {
                if (parse_submodule_params(&default_diff_options, value))
                        warning(_("Unknown value for 'diff.submodule' config variable: '%s'"),
                                value);
                return 0;
        }

        if (!strcmp(var, "diff.algorithm")) {
                diff_algorithm = parse_algorithm_value(value);
                if (diff_algorithm < 0)
                        return -1;
                return 0;
        }

        if (git_color_config(var, value, cb) < 0)
                return -1;

        return git_diff_basic_config(var, value, cb);
}

int git_diff_basic_config(const char *var, const char *value, void *cb)
{
        const char *name;

        if (!strcmp(var, "diff.renamelimit")) {
                diff_rename_limit_default = git_config_int(var, value);
                return 0;
        }

        if (userdiff_config(var, value) < 0)
                return -1;

        if (skip_prefix(var, "diff.color.", &name) ||
            skip_prefix(var, "color.diff.", &name)) {
                int slot = parse_diff_color_slot(name);
                if (slot < 0)
                        return 0;
                if (!value)
                        return config_error_nonbool(var);
                return color_parse(value, diff_colors[slot]);
        }

        /* like GNU diff's --suppress-blank-empty option  */
        if (!strcmp(var, "diff.suppressblankempty") ||
                        /* for backwards compatibility */
                        !strcmp(var, "diff.suppress-blank-empty")) {
                diff_suppress_blank_empty = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "diff.dirstat")) {
                struct strbuf errmsg = STRBUF_INIT;
                default_diff_options.dirstat_permille = diff_dirstat_permille_default;
                if (parse_dirstat_params(&default_diff_options, value, &errmsg))
                        warning(_("Found errors in 'diff.dirstat' config variable:\n%s"),
                                errmsg.buf);
                strbuf_release(&errmsg);
                diff_dirstat_permille_default = default_diff_options.dirstat_permille;
                return 0;
        }

        if (starts_with(var, "submodule."))
                return parse_submodule_config_option(var, value);

        return git_default_config(var, value, cb);
}

static char *quote_two(const char *one, const char *two)
{
        int need_one = quote_c_style(one, NULL, NULL, 1);
        int need_two = quote_c_style(two, NULL, NULL, 1);
        struct strbuf res = STRBUF_INIT;

        if (need_one + need_two) {
                strbuf_addch(&res, '"');
                quote_c_style(one, &res, NULL, 1);
                quote_c_style(two, &res, NULL, 1);
                strbuf_addch(&res, '"');
        } else {
                strbuf_addstr(&res, one);
                strbuf_addstr(&res, two);
        }
        return strbuf_detach(&res, NULL);
}

static const char *external_diff(void)
{
        static const char *external_diff_cmd = NULL;
        static int done_preparing = 0;

        if (done_preparing)
                return external_diff_cmd;
        external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
        if (!external_diff_cmd)
                external_diff_cmd = external_diff_cmd_cfg;
        done_preparing = 1;
        return external_diff_cmd;
}

/*
 * Keep track of files used for diffing. Sometimes such an entry
 * refers to a temporary file, sometimes to an existing file, and
 * sometimes to "/dev/null".
 */
static struct diff_tempfile {
        /*
         * filename external diff should read from, or NULL if this
         * entry is currently not in use:
         */
        const char *name;

        char hex[GIT_SHA1_HEXSZ + 1];
        char mode[10];

        /*
         * If this diff_tempfile instance refers to a temporary file,
         * this tempfile object is used to manage its lifetime.
         */
        struct tempfile tempfile;
} diff_temp[2];

typedef unsigned long (*sane_truncate_fn)(char *line, unsigned long len);

struct emit_callback {
        int color_diff;
        unsigned ws_rule;
        int blank_at_eof_in_preimage;
        int blank_at_eof_in_postimage;
        int lno_in_preimage;
        int lno_in_postimage;
        sane_truncate_fn truncate;
        const char **label_path;
        struct diff_words_data *diff_words;
        struct diff_options *opt;
        int *found_changesp;
        struct strbuf *header;
};

static int count_lines(const char *data, int size)
{
        int count, ch, completely_empty = 1, nl_just_seen = 0;
        count = 0;
        while (0 < size--) {
                ch = *data++;
                if (ch == '\n') {
                        count++;
                        nl_just_seen = 1;
                        completely_empty = 0;
                }
                else {
                        nl_just_seen = 0;
                        completely_empty = 0;
                }
        }
        if (completely_empty)
                return 0;
        if (!nl_just_seen)
                count++; /* no trailing newline */
        return count;
}

static int fill_mmfile(mmfile_t *mf, struct diff_filespec *one)
{
        if (!DIFF_FILE_VALID(one)) {
                mf->ptr = (char *)""; /* does not matter */
                mf->size = 0;
                return 0;
        }
        else if (diff_populate_filespec(one, 0))
                return -1;

        mf->ptr = one->data;
        mf->size = one->size;
        return 0;
}

/* like fill_mmfile, but only for size, so we can avoid retrieving blob */
static unsigned long diff_filespec_size(struct diff_filespec *one)
{
        if (!DIFF_FILE_VALID(one))
                return 0;
        diff_populate_filespec(one, CHECK_SIZE_ONLY);
        return one->size;
}

static int count_trailing_blank(mmfile_t *mf, unsigned ws_rule)
{
        char *ptr = mf->ptr;
        long size = mf->size;
        int cnt = 0;

        if (!size)
                return cnt;
        ptr += size - 1; /* pointing at the very end */
        if (*ptr != '\n')
                ; /* incomplete line */
        else
                ptr--; /* skip the last LF */
        while (mf->ptr < ptr) {
                char *prev_eol;
                for (prev_eol = ptr; mf->ptr <= prev_eol; prev_eol--)
                        if (*prev_eol == '\n')
                                break;
                if (!ws_blank_line(prev_eol + 1, ptr - prev_eol, ws_rule))
                        break;
                cnt++;
                ptr = prev_eol - 1;
        }
        return cnt;
}

static void check_blank_at_eof(mmfile_t *mf1, mmfile_t *mf2,
                               struct emit_callback *ecbdata)
{
        int l1, l2, at;
        unsigned ws_rule = ecbdata->ws_rule;
        l1 = count_trailing_blank(mf1, ws_rule);
        l2 = count_trailing_blank(mf2, ws_rule);
        if (l2 <= l1) {
                ecbdata->blank_at_eof_in_preimage = 0;
                ecbdata->blank_at_eof_in_postimage = 0;
                return;
        }
        at = count_lines(mf1->ptr, mf1->size);
        ecbdata->blank_at_eof_in_preimage = (at - l1) + 1;

        at = count_lines(mf2->ptr, mf2->size);
        ecbdata->blank_at_eof_in_postimage = (at - l2) + 1;
}

static void emit_line_0(struct diff_options *o, const char *set, const char *reset,
                        int first, const char *line, int len)
{
        int has_trailing_newline, has_trailing_carriage_return;
        int nofirst;
        FILE *file = o->file;

        fputs(diff_line_prefix(o), file);

        if (len == 0) {
                has_trailing_newline = (first == '\n');
                has_trailing_carriage_return = (!has_trailing_newline &&
                                                (first == '\r'));
                nofirst = has_trailing_newline || has_trailing_carriage_return;
        } else {
                has_trailing_newline = (len > 0 && line[len-1] == '\n');
                if (has_trailing_newline)
                        len--;
                has_trailing_carriage_return = (len > 0 && line[len-1] == '\r');
                if (has_trailing_carriage_return)
                        len--;
                nofirst = 0;
        }

        if (len || !nofirst) {
                fputs(set, file);
                if (!nofirst)
                        fputc(first, file);
                fwrite(line, len, 1, file);
                fputs(reset, file);
        }
        if (has_trailing_carriage_return)
                fputc('\r', file);
        if (has_trailing_newline)
                fputc('\n', file);
}

static void emit_line(struct diff_options *o, const char *set, const char *reset,
                      const char *line, int len)
{
        emit_line_0(o, set, reset, line[0], line+1, len-1);
}

static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line, int len)
{
        if (!((ecbdata->ws_rule & WS_BLANK_AT_EOF) &&
              ecbdata->blank_at_eof_in_preimage &&
              ecbdata->blank_at_eof_in_postimage &&
              ecbdata->blank_at_eof_in_preimage <= ecbdata->lno_in_preimage &&
              ecbdata->blank_at_eof_in_postimage <= ecbdata->lno_in_postimage))
                return 0;
        return ws_blank_line(line, len, ecbdata->ws_rule);
}

static void emit_line_checked(const char *reset,
                              struct emit_callback *ecbdata,
                              const char *line, int len,
                              enum color_diff color,
                              unsigned ws_error_highlight,
                              char sign)
{
        const char *set = diff_get_color(ecbdata->color_diff, color);
        const char *ws = NULL;

        if (ecbdata->opt->ws_error_highlight & ws_error_highlight) {
                ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
                if (!*ws)
                        ws = NULL;
        }

        if (!ws)
                emit_line_0(ecbdata->opt, set, reset, sign, line, len);
        else if (sign == '+' && new_blank_line_at_eof(ecbdata, line, len))
                /* Blank line at EOF - paint '+' as well */
                emit_line_0(ecbdata->opt, ws, reset, sign, line, len);
        else {
                /* Emit just the prefix, then the rest. */
                emit_line_0(ecbdata->opt, set, reset, sign, "", 0);
                ws_check_emit(line, len, ecbdata->ws_rule,
                              ecbdata->opt->file, set, reset, ws);
        }
}

static void emit_add_line(const char *reset,
                          struct emit_callback *ecbdata,
                          const char *line, int len)
{
        emit_line_checked(reset, ecbdata, line, len,
                          DIFF_FILE_NEW, WSEH_NEW, '+');
}

static void emit_del_line(const char *reset,
                          struct emit_callback *ecbdata,
                          const char *line, int len)
{
        emit_line_checked(reset, ecbdata, line, len,
                          DIFF_FILE_OLD, WSEH_OLD, '-');
}

static void emit_context_line(const char *reset,
                              struct emit_callback *ecbdata,
                              const char *line, int len)
{
        emit_line_checked(reset, ecbdata, line, len,
                          DIFF_CONTEXT, WSEH_CONTEXT, ' ');
}

static void emit_hunk_header(struct emit_callback *ecbdata,
                             const char *line, int len)
{
        const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
        const char *frag = diff_get_color(ecbdata->color_diff, DIFF_FRAGINFO);
        const char *func = diff_get_color(ecbdata->color_diff, DIFF_FUNCINFO);
        const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
        static const char atat[2] = { '@', '@' };
        const char *cp, *ep;
        struct strbuf msgbuf = STRBUF_INIT;
        int org_len = len;
        int i = 1;

        /*
         * As a hunk header must begin with "@@ -<old>, +<new> @@",
         * it always is at least 10 bytes long.
         */
        if (len < 10 ||
            memcmp(line, atat, 2) ||
            !(ep = memmem(line + 2, len - 2, atat, 2))) {
                emit_line(ecbdata->opt, context, reset, line, len);
                return;
        }
        ep += 2; /* skip over @@ */

        /* The hunk header in fraginfo color */
        strbuf_addstr(&msgbuf, frag);
        strbuf_add(&msgbuf, line, ep - line);
        strbuf_addstr(&msgbuf, reset);

        /*
         * trailing "\r\n"
         */
        for ( ; i < 3; i++)
                if (line[len - i] == '\r' || line[len - i] == '\n')
                        len--;

        /* blank before the func header */
        for (cp = ep; ep - line < len; ep++)
                if (*ep != ' ' && *ep != '\t')
                        break;
        if (ep != cp) {
                strbuf_addstr(&msgbuf, context);
                strbuf_add(&msgbuf, cp, ep - cp);
                strbuf_addstr(&msgbuf, reset);
        }

        if (ep < line + len) {
                strbuf_addstr(&msgbuf, func);
                strbuf_add(&msgbuf, ep, line + len - ep);
                strbuf_addstr(&msgbuf, reset);
        }

        strbuf_add(&msgbuf, line + len, org_len - len);
        emit_line(ecbdata->opt, "", "", msgbuf.buf, msgbuf.len);
        strbuf_release(&msgbuf);
}

static struct diff_tempfile *claim_diff_tempfile(void) {
        int i;
        for (i = 0; i < ARRAY_SIZE(diff_temp); i++)
                if (!diff_temp[i].name)
                        return diff_temp + i;
        die("BUG: diff is failing to clean up its tempfiles");
}

static void remove_tempfile(void)
{
        int i;
        for (i = 0; i < ARRAY_SIZE(diff_temp); i++) {
                if (is_tempfile_active(&diff_temp[i].tempfile))
                        delete_tempfile(&diff_temp[i].tempfile);
                diff_temp[i].name = NULL;
        }
}

static void print_line_count(FILE *file, int count)
{
        switch (count) {
        case 0:
                fprintf(file, "0,0");
                break;
        case 1:
                fprintf(file, "1");
                break;
        default:
                fprintf(file, "1,%d", count);
                break;
        }
}

static void emit_rewrite_lines(struct emit_callback *ecb,
                               int prefix, const char *data, int size)
{
        const char *endp = NULL;
        static const char *nneof = " No newline at end of file\n";
        const char *reset = diff_get_color(ecb->color_diff, DIFF_RESET);

        while (0 < size) {
                int len;

                endp = memchr(data, '\n', size);
                len = endp ? (endp - data + 1) : size;
                if (prefix != '+') {
                        ecb->lno_in_preimage++;
                        emit_del_line(reset, ecb, data, len);
                } else {
                        ecb->lno_in_postimage++;
                        emit_add_line(reset, ecb, data, len);
                }
                size -= len;
                data += len;
        }
        if (!endp) {
                const char *context = diff_get_color(ecb->color_diff,
                                                     DIFF_CONTEXT);
                putc('\n', ecb->opt->file);
                emit_line_0(ecb->opt, context, reset, '\\',
                            nneof, strlen(nneof));
        }
}

static void emit_rewrite_diff(const char *name_a,
                              const char *name_b,
                              struct diff_filespec *one,
                              struct diff_filespec *two,
                              struct userdiff_driver *textconv_one,
                              struct userdiff_driver *textconv_two,
                              struct diff_options *o)
{
        int lc_a, lc_b;
        const char *name_a_tab, *name_b_tab;
        const char *metainfo = diff_get_color(o->use_color, DIFF_METAINFO);
        const char *fraginfo = diff_get_color(o->use_color, DIFF_FRAGINFO);
        const char *reset = diff_get_color(o->use_color, DIFF_RESET);
        static struct strbuf a_name = STRBUF_INIT, b_name = STRBUF_INIT;
        const char *a_prefix, *b_prefix;
        char *data_one, *data_two;
        size_t size_one, size_two;
        struct emit_callback ecbdata;
        const char *line_prefix = diff_line_prefix(o);

        if (diff_mnemonic_prefix && DIFF_OPT_TST(o, REVERSE_DIFF)) {
                a_prefix = o->b_prefix;
                b_prefix = o->a_prefix;
        } else {
                a_prefix = o->a_prefix;
                b_prefix = o->b_prefix;
        }

        name_a += (*name_a == '/');
        name_b += (*name_b == '/');
        name_a_tab = strchr(name_a, ' ') ? "\t" : "";
        name_b_tab = strchr(name_b, ' ') ? "\t" : "";

        strbuf_reset(&a_name);
        strbuf_reset(&b_name);
        quote_two_c_style(&a_name, a_prefix, name_a, 0);
        quote_two_c_style(&b_name, b_prefix, name_b, 0);

        size_one = fill_textconv(textconv_one, one, &data_one);
        size_two = fill_textconv(textconv_two, two, &data_two);

        memset(&ecbdata, 0, sizeof(ecbdata));
        ecbdata.color_diff = want_color(o->use_color);
        ecbdata.found_changesp = &o->found_changes;
        ecbdata.ws_rule = whitespace_rule(name_b);
        ecbdata.opt = o;
        if (ecbdata.ws_rule & WS_BLANK_AT_EOF) {
                mmfile_t mf1, mf2;
                mf1.ptr = (char *)data_one;
                mf2.ptr = (char *)data_two;
                mf1.size = size_one;
                mf2.size = size_two;
                check_blank_at_eof(&mf1, &mf2, &ecbdata);
        }
        ecbdata.lno_in_preimage = 1;
        ecbdata.lno_in_postimage = 1;

        lc_a = count_lines(data_one, size_one);
        lc_b = count_lines(data_two, size_two);
        fprintf(o->file,
                "%s%s--- %s%s%s\n%s%s+++ %s%s%s\n%s%s@@ -",
                line_prefix, metainfo, a_name.buf, name_a_tab, reset,
                line_prefix, metainfo, b_name.buf, name_b_tab, reset,
                line_prefix, fraginfo);
        if (!o->irreversible_delete)
                print_line_count(o->file, lc_a);
        else
                fprintf(o->file, "?,?");
        fprintf(o->file, " +");
        print_line_count(o->file, lc_b);
        fprintf(o->file, " @@%s\n", reset);
        if (lc_a && !o->irreversible_delete)
                emit_rewrite_lines(&ecbdata, '-', data_one, size_one);
        if (lc_b)
                emit_rewrite_lines(&ecbdata, '+', data_two, size_two);
        if (textconv_one)
                free((char *)data_one);
        if (textconv_two)
                free((char *)data_two);
}

struct diff_words_buffer {
        mmfile_t text;
        long alloc;
        struct diff_words_orig {
                const char *begin, *end;
        } *orig;
        int orig_nr, orig_alloc;
};

static void diff_words_append(char *line, unsigned long len,
                struct diff_words_buffer *buffer)
{
        ALLOC_GROW(buffer->text.ptr, buffer->text.size + len, buffer->alloc);
        line++;
        len--;
        memcpy(buffer->text.ptr + buffer->text.size, line, len);
        buffer->text.size += len;
        buffer->text.ptr[buffer->text.size] = '\0';
}

struct diff_words_style_elem {
        const char *prefix;
        const char *suffix;
        const char *color; /* NULL; filled in by the setup code if
                            * color is enabled */
};

struct diff_words_style {
        enum diff_words_type type;
        struct diff_words_style_elem new, old, ctx;
        const char *newline;
};

static struct diff_words_style diff_words_styles[] = {
        { DIFF_WORDS_PORCELAIN, {"+", "\n"}, {"-", "\n"}, {" ", "\n"}, "~\n" },
        { DIFF_WORDS_PLAIN, {"{+", "+}"}, {"[-", "-]"}, {"", ""}, "\n" },
        { DIFF_WORDS_COLOR, {"", ""}, {"", ""}, {"", ""}, "\n" }
};

struct diff_words_data {
        struct diff_words_buffer minus, plus;
        const char *current_plus;
        int last_minus;
        struct diff_options *opt;
        regex_t *word_regex;
        enum diff_words_type type;
        struct diff_words_style *style;
};

static int fn_out_diff_words_write_helper(FILE *fp,
                                          struct diff_words_style_elem *st_el,
                                          const char *newline,
                                          size_t count, const char *buf,
                                          const char *line_prefix)
{
        int print = 0;

        while (count) {
                char *p = memchr(buf, '\n', count);
                if (print)
                        fputs(line_prefix, fp);
                if (p != buf) {
                        if (st_el->color && fputs(st_el->color, fp) < 0)
                                return -1;
                        if (fputs(st_el->prefix, fp) < 0 ||
                            fwrite(buf, p ? p - buf : count, 1, fp) != 1 ||
                            fputs(st_el->suffix, fp) < 0)
                                return -1;
                        if (st_el->color && *st_el->color
                            && fputs(GIT_COLOR_RESET, fp) < 0)
                                return -1;
                }
                if (!p)
                        return 0;
                if (fputs(newline, fp) < 0)
                        return -1;
                count -= p + 1 - buf;
                buf = p + 1;
                print = 1;
        }
        return 0;
}

/*
 * '--color-words' algorithm can be described as:
 *
 *   1. collect a the minus/plus lines of a diff hunk, divided into
 *      minus-lines and plus-lines;
 *
 *   2. break both minus-lines and plus-lines into words and
 *      place them into two mmfile_t with one word for each line;
 *
 *   3. use xdiff to run diff on the two mmfile_t to get the words level diff;
 *
 * And for the common parts of the both file, we output the plus side text.
 * diff_words->current_plus is used to trace the current position of the plus file
 * which printed. diff_words->last_minus is used to trace the last minus word
 * printed.
 *
 * For '--graph' to work with '--color-words', we need to output the graph prefix
 * on each line of color words output. Generally, there are two conditions on
 * which we should output the prefix.
 *
 *   1. diff_words->last_minus == 0 &&
 *      diff_words->current_plus == diff_words->plus.text.ptr
 *
 *      that is: the plus text must start as a new line, and if there is no minus
 *      word printed, a graph prefix must be printed.
 *
 *   2. diff_words->current_plus > diff_words->plus.text.ptr &&
 *      *(diff_words->current_plus - 1) == '\n'
 *
 *      that is: a graph prefix must be printed following a '\n'
 */
static int color_words_output_graph_prefix(struct diff_words_data *diff_words)
{
        if ((diff_words->last_minus == 0 &&
                diff_words->current_plus == diff_words->plus.text.ptr) ||
                (diff_words->current_plus > diff_words->plus.text.ptr &&
                *(diff_words->current_plus - 1) == '\n')) {
                return 1;
        } else {
                return 0;
        }
}

static void fn_out_diff_words_aux(void *priv, char *line, unsigned long len)
{
        struct diff_words_data *diff_words = priv;
        struct diff_words_style *style = diff_words->style;
        int minus_first, minus_len, plus_first, plus_len;
        const char *minus_begin, *minus_end, *plus_begin, *plus_end;
        struct diff_options *opt = diff_words->opt;
        const char *line_prefix;

        if (line[0] != '@' || parse_hunk_header(line, len,
                        &minus_first, &minus_len, &plus_first, &plus_len))
                return;

        assert(opt);
        line_prefix = diff_line_prefix(opt);

        /* POSIX requires that first be decremented by one if len == 0... */
        if (minus_len) {
                minus_begin = diff_words->minus.orig[minus_first].begin;
                minus_end =
                        diff_words->minus.orig[minus_first + minus_len - 1].end;
        } else
                minus_begin = minus_end =
                        diff_words->minus.orig[minus_first].end;

        if (plus_len) {
                plus_begin = diff_words->plus.orig[plus_first].begin;
                plus_end = diff_words->plus.orig[plus_first + plus_len - 1].end;
        } else
                plus_begin = plus_end = diff_words->plus.orig[plus_first].end;

        if (color_words_output_graph_prefix(diff_words)) {
                fputs(line_prefix, diff_words->opt->file);
        }
        if (diff_words->current_plus != plus_begin) {
                fn_out_diff_words_write_helper(diff_words->opt->file,
                                &style->ctx, style->newline,
                                plus_begin - diff_words->current_plus,
                                diff_words->current_plus, line_prefix);
                if (*(plus_begin - 1) == '\n')
                        fputs(line_prefix, diff_words->opt->file);
        }
        if (minus_begin != minus_end) {
                fn_out_diff_words_write_helper(diff_words->opt->file,
                                &style->old, style->newline,
                                minus_end - minus_begin, minus_begin,
                                line_prefix);
        }
        if (plus_begin != plus_end) {
                fn_out_diff_words_write_helper(diff_words->opt->file,
                                &style->new, style->newline,
                                plus_end - plus_begin, plus_begin,
                                line_prefix);
        }

        diff_words->current_plus = plus_end;
        diff_words->last_minus = minus_first;
}

/* This function starts looking at *begin, and returns 0 iff a word was found. */
static int find_word_boundaries(mmfile_t *buffer, regex_t *word_regex,
                int *begin, int *end)
{
        if (word_regex && *begin < buffer->size) {
                regmatch_t match[1];
                if (!regexec(word_regex, buffer->ptr + *begin, 1, match, 0)) {
                        char *p = memchr(buffer->ptr + *begin + match[0].rm_so,
                                        '\n', match[0].rm_eo - match[0].rm_so);
                        *end = p ? p - buffer->ptr : match[0].rm_eo + *begin;
                        *begin += match[0].rm_so;
                        return *begin >= *end;
                }
                return -1;
        }

        /* find the next word */
        while (*begin < buffer->size && isspace(buffer->ptr[*begin]))
                (*begin)++;
        if (*begin >= buffer->size)
                return -1;

        /* find the end of the word */
        *end = *begin + 1;
        while (*end < buffer->size && !isspace(buffer->ptr[*end]))
                (*end)++;

        return 0;
}

/*
 * This function splits the words in buffer->text, stores the list with
 * newline separator into out, and saves the offsets of the original words
 * in buffer->orig.
 */
static void diff_words_fill(struct diff_words_buffer *buffer, mmfile_t *out,
                regex_t *word_regex)
{
        int i, j;
        long alloc = 0;

        out->size = 0;
        out->ptr = NULL;

        /* fake an empty "0th" word */
        ALLOC_GROW(buffer->orig, 1, buffer->orig_alloc);
        buffer->orig[0].begin = buffer->orig[0].end = buffer->text.ptr;
        buffer->orig_nr = 1;

        for (i = 0; i < buffer->text.size; i++) {
                if (find_word_boundaries(&buffer->text, word_regex, &i, &j))
                        return;

                /* store original boundaries */
                ALLOC_GROW(buffer->orig, buffer->orig_nr + 1,
                                buffer->orig_alloc);
                buffer->orig[buffer->orig_nr].begin = buffer->text.ptr + i;
                buffer->orig[buffer->orig_nr].end = buffer->text.ptr + j;
                buffer->orig_nr++;

                /* store one word */
                ALLOC_GROW(out->ptr, out->size + j - i + 1, alloc);
                memcpy(out->ptr + out->size, buffer->text.ptr + i, j - i);
                out->ptr[out->size + j - i] = '\n';
                out->size += j - i + 1;

                i = j - 1;
        }
}

/* this executes the word diff on the accumulated buffers */
static void diff_words_show(struct diff_words_data *diff_words)
{
        xpparam_t xpp;
        xdemitconf_t xecfg;
        mmfile_t minus, plus;
        struct diff_words_style *style = diff_words->style;

        struct diff_options *opt = diff_words->opt;
        const char *line_prefix;

        assert(opt);
        line_prefix = diff_line_prefix(opt);

        /* special case: only removal */
        if (!diff_words->plus.text.size) {
                fputs(line_prefix, diff_words->opt->file);
                fn_out_diff_words_write_helper(diff_words->opt->file,
                        &style->old, style->newline,
                        diff_words->minus.text.size,
                        diff_words->minus.text.ptr, line_prefix);
                diff_words->minus.text.size = 0;
                return;
        }

        diff_words->current_plus = diff_words->plus.text.ptr;
        diff_words->last_minus = 0;

        memset(&xpp, 0, sizeof(xpp));
        memset(&xecfg, 0, sizeof(xecfg));
        diff_words_fill(&diff_words->minus, &minus, diff_words->word_regex);
        diff_words_fill(&diff_words->plus, &plus, diff_words->word_regex);
        xpp.flags = 0;
        /* as only the hunk header will be parsed, we need a 0-context */
        xecfg.ctxlen = 0;
        if (xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, diff_words,
                          &xpp, &xecfg))
                die("unable to generate word diff");
        free(minus.ptr);
        free(plus.ptr);
        if (diff_words->current_plus != diff_words->plus.text.ptr +
                        diff_words->plus.text.size) {
                if (color_words_output_graph_prefix(diff_words))
                        fputs(line_prefix, diff_words->opt->file);
                fn_out_diff_words_write_helper(diff_words->opt->file,
                        &style->ctx, style->newline,
                        diff_words->plus.text.ptr + diff_words->plus.text.size
                        - diff_words->current_plus, diff_words->current_plus,
                        line_prefix);
        }
        diff_words->minus.text.size = diff_words->plus.text.size = 0;
}

/* In "color-words" mode, show word-diff of words accumulated in the buffer */
static void diff_words_flush(struct emit_callback *ecbdata)
{
        if (ecbdata->diff_words->minus.text.size ||
            ecbdata->diff_words->plus.text.size)
                diff_words_show(ecbdata->diff_words);
}

static void diff_filespec_load_driver(struct diff_filespec *one)
{
        /* Use already-loaded driver */
        if (one->driver)
                return;

        if (S_ISREG(one->mode))
                one->driver = userdiff_find_by_path(one->path);

        /* Fallback to default settings */
        if (!one->driver)
                one->driver = userdiff_find_by_name("default");
}

static const char *userdiff_word_regex(struct diff_filespec *one)
{
        diff_filespec_load_driver(one);
        return one->driver->word_regex;
}

static void init_diff_words_data(struct emit_callback *ecbdata,
                                 struct diff_options *orig_opts,
                                 struct diff_filespec *one,
                                 struct diff_filespec *two)
{
        int i;
        struct diff_options *o = xmalloc(sizeof(struct diff_options));
        memcpy(o, orig_opts, sizeof(struct diff_options));

        ecbdata->diff_words =
                xcalloc(1, sizeof(struct diff_words_data));
        ecbdata->diff_words->type = o->word_diff;
        ecbdata->diff_words->opt = o;
        if (!o->word_regex)
                o->word_regex = userdiff_word_regex(one);
        if (!o->word_regex)
                o->word_regex = userdiff_word_regex(two);
        if (!o->word_regex)
                o->word_regex = diff_word_regex_cfg;
        if (o->word_regex) {
                ecbdata->diff_words->word_regex = (regex_t *)
                        xmalloc(sizeof(regex_t));
                if (regcomp(ecbdata->diff_words->word_regex,
                            o->word_regex,
                            REG_EXTENDED | REG_NEWLINE))
                        die ("Invalid regular expression: %s",
                             o->word_regex);
        }
        for (i = 0; i < ARRAY_SIZE(diff_words_styles); i++) {
                if (o->word_diff == diff_words_styles[i].type) {
                        ecbdata->diff_words->style =
                                &diff_words_styles[i];
                        break;
                }
        }
        if (want_color(o->use_color)) {
                struct diff_words_style *st = ecbdata->diff_words->style;
                st->old.color = diff_get_color_opt(o, DIFF_FILE_OLD);
                st->new.color = diff_get_color_opt(o, DIFF_FILE_NEW);
                st->ctx.color = diff_get_color_opt(o, DIFF_CONTEXT);
        }
}

static void free_diff_words_data(struct emit_callback *ecbdata)
{
        if (ecbdata->diff_words) {
                diff_words_flush(ecbdata);
                free (ecbdata->diff_words->opt);
                free (ecbdata->diff_words->minus.text.ptr);
                free (ecbdata->diff_words->minus.orig);
                free (ecbdata->diff_words->plus.text.ptr);
                free (ecbdata->diff_words->plus.orig);
                if (ecbdata->diff_words->word_regex) {
                        regfree(ecbdata->diff_words->word_regex);
                        free(ecbdata->diff_words->word_regex);
                }
                free(ecbdata->diff_words);
                ecbdata->diff_words = NULL;
        }
}

const char *diff_get_color(int diff_use_color, enum color_diff ix)
{
        if (want_color(diff_use_color))
                return diff_colors[ix];
        return "";
}

const char *diff_line_prefix(struct diff_options *opt)
{
        struct strbuf *msgbuf;
        if (!opt->output_prefix)
                return "";

        msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
        return msgbuf->buf;
}

static unsigned long sane_truncate_line(struct emit_callback *ecb, char *line, unsigned long len)
{
        const char *cp;
        unsigned long allot;
        size_t l = len;

        if (ecb->truncate)
                return ecb->truncate(line, len);
        cp = line;
        allot = l;
        while (0 < l) {
                (void) utf8_width(&cp, &l);
                if (!cp)
                        break; /* truncated in the middle? */
        }
        return allot - l;
}

static void find_lno(const char *line, struct emit_callback *ecbdata)
{
        const char *p;
        ecbdata->lno_in_preimage = 0;
        ecbdata->lno_in_postimage = 0;
        p = strchr(line, '-');
        if (!p)
                return; /* cannot happen */
        ecbdata->lno_in_preimage = strtol(p + 1, NULL, 10);
        p = strchr(p, '+');
        if (!p)
                return; /* cannot happen */
        ecbdata->lno_in_postimage = strtol(p + 1, NULL, 10);
}

static void fn_out_consume(void *priv, char *line, unsigned long len)
{
        struct emit_callback *ecbdata = priv;
        const char *meta = diff_get_color(ecbdata->color_diff, DIFF_METAINFO);
        const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
        const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
        struct diff_options *o = ecbdata->opt;
        const char *line_prefix = diff_line_prefix(o);

        if (ecbdata->header) {
                fprintf(ecbdata->opt->file, "%s", ecbdata->header->buf);
                strbuf_reset(ecbdata->header);
                ecbdata->header = NULL;
        }
        *(ecbdata->found_changesp) = 1;

        if (ecbdata->label_path[0]) {
                const char *name_a_tab, *name_b_tab;

                name_a_tab = strchr(ecbdata->label_path[0], ' ') ? "\t" : "";
                name_b_tab = strchr(ecbdata->label_path[1], ' ') ? "\t" : "";

                fprintf(ecbdata->opt->file, "%s%s--- %s%s%s\n",
                        line_prefix, meta, ecbdata->label_path[0], reset, name_a_tab);
                fprintf(ecbdata->opt->file, "%s%s+++ %s%s%s\n",
                        line_prefix, meta, ecbdata->label_path[1], reset, name_b_tab);
                ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
        }

        if (diff_suppress_blank_empty
            && len == 2 && line[0] == ' ' && line[1] == '\n') {
                line[0] = '\n';
                len = 1;
        }

        if (line[0] == '@') {
                if (ecbdata->diff_words)
                        diff_words_flush(ecbdata);
                len = sane_truncate_line(ecbdata, line, len);
                find_lno(line, ecbdata);
                emit_hunk_header(ecbdata, line, len);
                if (line[len-1] != '\n')
                        putc('\n', ecbdata->opt->file);
                return;
        }

        if (len < 1) {
                emit_line(ecbdata->opt, reset, reset, line, len);
                if (ecbdata->diff_words
                    && ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN)
                        fputs("~\n", ecbdata->opt->file);
                return;
        }

        if (ecbdata->diff_words) {
                if (line[0] == '-') {
                        diff_words_append(line, len,
                                          &ecbdata->diff_words->minus);
                        return;
                } else if (line[0] == '+') {
                        diff_words_append(line, len,
                                          &ecbdata->diff_words->plus);
                        return;
                } else if (starts_with(line, "\\ ")) {
                        /*
                         * Eat the "no newline at eof" marker as if we
                         * saw a "+" or "-" line with nothing on it,
                         * and return without diff_words_flush() to
                         * defer processing. If this is the end of
                         * preimage, more "+" lines may come after it.
                         */
                        return;
                }
                diff_words_flush(ecbdata);
                if (ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN) {
                        emit_line(ecbdata->opt, context, reset, line, len);
                        fputs("~\n", ecbdata->opt->file);
                } else {
                        /*
                         * Skip the prefix character, if any.  With
                         * diff_suppress_blank_empty, there may be
                         * none.
                         */
                        if (line[0] != '\n') {
                              line++;
                              len--;
                        }
                        emit_line(ecbdata->opt, context, reset, line, len);
                }
                return;
        }

        switch (line[0]) {
        case '+':
                ecbdata->lno_in_postimage++;
                emit_add_line(reset, ecbdata, line + 1, len - 1);
                break;
        case '-':
                ecbdata->lno_in_preimage++;
                emit_del_line(reset, ecbdata, line + 1, len - 1);
                break;
        case ' ':
                ecbdata->lno_in_postimage++;
                ecbdata->lno_in_preimage++;
                emit_context_line(reset, ecbdata, line + 1, len - 1);
                break;
        default:
                /* incomplete line at the end */
                ecbdata->lno_in_preimage++;
                emit_line(ecbdata->opt,
                          diff_get_color(ecbdata->color_diff, DIFF_CONTEXT),
                          reset, line, len);
                break;
        }
}

static char *pprint_rename(const char *a, const char *b)
{
        const char *old = a;
        const char *new = b;
        struct strbuf name = STRBUF_INIT;
        int pfx_length, sfx_length;
        int pfx_adjust_for_slash;
        int len_a = strlen(a);
        int len_b = strlen(b);
        int a_midlen, b_midlen;
        int qlen_a = quote_c_style(a, NULL, NULL, 0);
        int qlen_b = quote_c_style(b, NULL, NULL, 0);

        if (qlen_a || qlen_b) {
                quote_c_style(a, &name, NULL, 0);
                strbuf_addstr(&name, " => ");
                quote_c_style(b, &name, NULL, 0);
                return strbuf_detach(&name, NULL);
        }

        /* Find common prefix */
        pfx_length = 0;
        while (*old && *new && *old == *new) {
                if (*old == '/')
                        pfx_length = old - a + 1;
                old++;
                new++;
        }

        /* Find common suffix */
        old = a + len_a;
        new = b + len_b;
        sfx_length = 0;
        /*
         * If there is a common prefix, it must end in a slash.  In
         * that case we let this loop run 1 into the prefix to see the
         * same slash.
         *
         * If there is no common prefix, we cannot do this as it would
         * underrun the input strings.
         */
        pfx_adjust_for_slash = (pfx_length ? 1 : 0);
        while (a + pfx_length - pfx_adjust_for_slash <= old &&
               b + pfx_length - pfx_adjust_for_slash <= new &&
               *old == *new) {
                if (*old == '/')
                        sfx_length = len_a - (old - a);
                old--;
                new--;
        }

        /*
         * pfx{mid-a => mid-b}sfx
         * {pfx-a => pfx-b}sfx
         * pfx{sfx-a => sfx-b}
         * name-a => name-b
         */
        a_midlen = len_a - pfx_length - sfx_length;
        b_midlen = len_b - pfx_length - sfx_length;
        if (a_midlen < 0)
                a_midlen = 0;
        if (b_midlen < 0)
                b_midlen = 0;

        strbuf_grow(&name, pfx_length + a_midlen + b_midlen + sfx_length + 7);
        if (pfx_length + sfx_length) {
                strbuf_add(&name, a, pfx_length);
                strbuf_addch(&name, '{');
        }
        strbuf_add(&name, a + pfx_length, a_midlen);
        strbuf_addstr(&name, " => ");
        strbuf_add(&name, b + pfx_length, b_midlen);
        if (pfx_length + sfx_length) {
                strbuf_addch(&name, '}');
                strbuf_add(&name, a + len_a - sfx_length, sfx_length);
        }
        return strbuf_detach(&name, NULL);
}

struct diffstat_t {
        int nr;
        int alloc;
        struct diffstat_file {
                char *from_name;
                char *name;
                char *print_name;
                unsigned is_unmerged:1;
                unsigned is_binary:1;
                unsigned is_renamed:1;
                unsigned is_interesting:1;
                uintmax_t added, deleted;
        } **files;
};

static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
                                          const char *name_a,
                                          const char *name_b)
{
        struct diffstat_file *x;
        x = xcalloc(1, sizeof(*x));
        ALLOC_GROW(diffstat->files, diffstat->nr + 1, diffstat->alloc);
        diffstat->files[diffstat->nr++] = x;
        if (name_b) {
                x->from_name = xstrdup(name_a);
                x->name = xstrdup(name_b);
                x->is_renamed = 1;
        }
        else {
                x->from_name = NULL;
                x->name = xstrdup(name_a);
        }
        return x;
}

static void diffstat_consume(void *priv, char *line, unsigned long len)
{
        struct diffstat_t *diffstat = priv;
        struct diffstat_file *x = diffstat->files[diffstat->nr - 1];

        if (line[0] == '+')
                x->added++;
        else if (line[0] == '-')
                x->deleted++;
}

const char mime_boundary_leader[] = "------------";

static int scale_linear(int it, int width, int max_change)
{
        if (!it)
                return 0;
        /*
         * make sure that at least one '-' or '+' is printed if
         * there is any change to this path. The easiest way is to
         * scale linearly as if the alloted width is one column shorter
         * than it is, and then add 1 to the result.
         */
        return 1 + (it * (width - 1) / max_change);
}

static void show_name(FILE *file,
                      const char *prefix, const char *name, int len)
{
        fprintf(file, " %s%-*s |", prefix, len, name);
}

static void show_graph(FILE *file, char ch, int cnt, const char *set, const char *reset)
{
        if (cnt <= 0)
                return;
        fprintf(file, "%s", set);
        while (cnt--)
                putc(ch, file);
        fprintf(file, "%s", reset);
}

static void fill_print_name(struct diffstat_file *file)
{
        char *pname;

        if (file->print_name)
                return;

        if (!file->is_renamed) {
                struct strbuf buf = STRBUF_INIT;
                if (quote_c_style(file->name, &buf, NULL, 0)) {
                        pname = strbuf_detach(&buf, NULL);
                } else {
                        pname = file->name;
                        strbuf_release(&buf);
                }
        } else {
                pname = pprint_rename(file->from_name, file->name);
        }
        file->print_name = pname;
}

int print_stat_summary(FILE *fp, int files, int insertions, int deletions)
{
        struct strbuf sb = STRBUF_INIT;
        int ret;

        if (!files) {
                assert(insertions == 0 && deletions == 0);
                return fprintf(fp, "%s\n", " 0 files changed");
        }

        strbuf_addf(&sb,
                    (files == 1) ? " %d file changed" : " %d files changed",
                    files);

        /*
         * For binary diff, the caller may want to print "x files
         * changed" with insertions == 0 && deletions == 0.
         *
         * Not omitting "0 insertions(+), 0 deletions(-)" in this case
         * is probably less confusing (i.e skip over "2 files changed
         * but nothing about added/removed lines? Is this a bug in Git?").
         */
        if (insertions || deletions == 0) {
                strbuf_addf(&sb,
                            (insertions == 1) ? ", %d insertion(+)" : ", %d insertions(+)",
                            insertions);
        }

        if (deletions || insertions == 0) {
                strbuf_addf(&sb,
                            (deletions == 1) ? ", %d deletion(-)" : ", %d deletions(-)",
                            deletions);
        }
        strbuf_addch(&sb, '\n');
        ret = fputs(sb.buf, fp);
        strbuf_release(&sb);
        return ret;
}

static void show_stats(struct diffstat_t *data, struct diff_options *options)
{
        int i, len, add, del, adds = 0, dels = 0;
        uintmax_t max_change = 0, max_len = 0;
        int total_files = data->nr, count;
        int width, name_width, graph_width, number_width = 0, bin_width = 0;
        const char *reset, *add_c, *del_c;
        const char *line_prefix = "";
        int extra_shown = 0;

        if (data->nr == 0)
                return;

        line_prefix = diff_line_prefix(options);
        count = options->stat_count ? options->stat_count : data->nr;

        reset = diff_get_color_opt(options, DIFF_RESET);
        add_c = diff_get_color_opt(options, DIFF_FILE_NEW);
        del_c = diff_get_color_opt(options, DIFF_FILE_OLD);

        /*
         * Find the longest filename and max number of changes
         */
        for (i = 0; (i < count) && (i < data->nr); i++) {
                struct diffstat_file *file = data->files[i];
                uintmax_t change = file->added + file->deleted;

                if (!file->is_interesting && (change == 0)) {
                        count++; /* not shown == room for one more */
                        continue;
                }
                fill_print_name(file);
                len = strlen(file->print_name);
                if (max_len < len)
                        max_len = len;

                if (file->is_unmerged) {
                        /* "Unmerged" is 8 characters */
                        bin_width = bin_width < 8 ? 8 : bin_width;
                        continue;
                }
                if (file->is_binary) {
                        /* "Bin XXX -> YYY bytes" */
                        int w = 14 + decimal_width(file->added)
                                + decimal_width(file->deleted);
                        bin_width = bin_width < w ? w : bin_width;
                        /* Display change counts aligned with "Bin" */
                        number_width = 3;
                        continue;
                }

                if (max_change < change)
                        max_change = change;
        }
        count = i; /* where we can stop scanning in data->files[] */

        /*
         * We have width = stat_width or term_columns() columns total.
         * We want a maximum of min(max_len, stat_name_width) for the name part.
         * We want a maximum of min(max_change, stat_graph_width) for the +- part.
         * We also need 1 for " " and 4 + decimal_width(max_change)
         * for " | NNNN " and one the empty column at the end, altogether
         * 6 + decimal_width(max_change).
         *
         * If there's not enough space, we will use the smaller of
         * stat_name_width (if set) and 5/8*width for the filename,
         * and the rest for constant elements + graph part, but no more
         * than stat_graph_width for the graph part.
         * (5/8 gives 50 for filename and 30 for the constant parts + graph
         * for the standard terminal size).
         *
         * In other words: stat_width limits the maximum width, and
         * stat_name_width fixes the maximum width of the filename,
         * and is also used to divide available columns if there
         * aren't enough.
         *
         * Binary files are displayed with "Bin XXX -> YYY bytes"
         * instead of the change count and graph. This part is treated
         * similarly to the graph part, except that it is not
         * "scaled". If total width is too small to accommodate the
         * guaranteed minimum width of the filename part and the
         * separators and this message, this message will "overflow"
         * making the line longer than the maximum width.
         */

        if (options->stat_width == -1)
                width = term_columns() - strlen(line_prefix);
        else
                width = options->stat_width ? options->stat_width : 80;
        number_width = decimal_width(max_change) > number_width ?
                decimal_width(max_change) : number_width;

        if (options->stat_graph_width == -1)
                options->stat_graph_width = diff_stat_graph_width;

        /*
         * Guarantee 3/8*16==6 for the graph part
         * and 5/8*16==10 for the filename part
         */
        if (width < 16 + 6 + number_width)
                width = 16 + 6 + number_width;

        /*
         * First assign sizes that are wanted, ignoring available width.
         * strlen("Bin XXX -> YYY bytes") == bin_width, and the part
         * starting from "XXX" should fit in graph_width.
         */
        graph_width = max_change + 4 > bin_width ? max_change : bin_width - 4;
        if (options->stat_graph_width &&
            options->stat_graph_width < graph_width)
                graph_width = options->stat_graph_width;

        name_width = (options->stat_name_width > 0 &&
                      options->stat_name_width < max_len) ?
                options->stat_name_width : max_len;

        /*
         * Adjust adjustable widths not to exceed maximum width
         */
        if (name_width + number_width + 6 + graph_width > width) {
                if (graph_width > width * 3/8 - number_width - 6) {
                        graph_width = width * 3/8 - number_width - 6;
                        if (graph_width < 6)
                                graph_width = 6;
                }

                if (options->stat_graph_width &&
                    graph_width > options->stat_graph_width)
                        graph_width = options->stat_graph_width;
                if (name_width > width - number_width - 6 - graph_width)
                        name_width = width - number_width - 6 - graph_width;
                else
                        graph_width = width - number_width - 6 - name_width;
        }

        /*
         * From here name_width is the width of the name area,
         * and graph_width is the width of the graph area.
         * max_change is used to scale graph properly.
         */
        for (i = 0; i < count; i++) {
                const char *prefix = "";
                struct diffstat_file *file = data->files[i];
                char *name = file->print_name;
                uintmax_t added = file->added;
                uintmax_t deleted = file->deleted;
                int name_len;

                if (!file->is_interesting && (added + deleted == 0))
                        continue;

                /*
                 * "scale" the filename
                 */
                len = name_width;
                name_len = strlen(name);
                if (name_width < name_len) {
                        char *slash;
                        prefix = "...";
                        len -= 3;
                        name += name_len - len;
                        slash = strchr(name, '/');
                        if (slash)
                                name = slash;
                }

                if (file->is_binary) {
                        fprintf(options->file, "%s", line_prefix);
                        show_name(options->file, prefix, name, len);
                        fprintf(options->file, " %*s", number_width, "Bin");
                        if (!added && !deleted) {
                                putc('\n', options->file);
                                continue;
                        }
                        fprintf(options->file, " %s%"PRIuMAX"%s",
                                del_c, deleted, reset);
                        fprintf(options->file, " -> ");
                        fprintf(options->file, "%s%"PRIuMAX"%s",
                                add_c, added, reset);
                        fprintf(options->file, " bytes");
                        fprintf(options->file, "\n");
                        continue;
                }
                else if (file->is_unmerged) {
                        fprintf(options->file, "%s", line_prefix);
                        show_name(options->file, prefix, name, len);
                        fprintf(options->file, " Unmerged\n");
                        continue;
                }

                /*
                 * scale the add/delete
                 */
                add = added;
                del = deleted;

                if (graph_width <= max_change) {
                        int total = scale_linear(add + del, graph_width, max_change);
                        if (total < 2 && add && del)
                                /* width >= 2 due to the sanity check */
                                total = 2;
                        if (add < del) {
                                add = scale_linear(add, graph_width, max_change);
                                del = total - add;
                        } else {
                                del = scale_linear(del, graph_width, max_change);
                                add = total - del;
                        }
                }
                fprintf(options->file, "%s", line_prefix);
                show_name(options->file, prefix, name, len);
                fprintf(options->file, " %*"PRIuMAX"%s",
                        number_width, added + deleted,
                        added + deleted ? " " : "");
                show_graph(options->file, '+', add, add_c, reset);
                show_graph(options->file, '-', del, del_c, reset);
                fprintf(options->file, "\n");
        }

        for (i = 0; i < data->nr; i++) {
                struct diffstat_file *file = data->files[i];
                uintmax_t added = file->added;
                uintmax_t deleted = file->deleted;

                if (file->is_unmerged ||
                    (!file->is_interesting && (added + deleted == 0))) {
                        total_files--;
                        continue;
                }

                if (!file->is_binary) {
                        adds += added;
                        dels += deleted;
                }
                if (i < count)
                        continue;
                if (!extra_shown)
                        fprintf(options->file, "%s ...\n", line_prefix);
                extra_shown = 1;
        }
        fprintf(options->file, "%s", line_prefix);
        print_stat_summary(options->file, total_files, adds, dels);
}

static void show_shortstats(struct diffstat_t *data, struct diff_options *options)
{
        int i, adds = 0, dels = 0, total_files = data->nr;

        if (data->nr == 0)
                return;

        for (i = 0; i < data->nr; i++) {
                int added = data->files[i]->added;
                int deleted= data->files[i]->deleted;

                if (data->files[i]->is_unmerged ||
                    (!data->files[i]->is_interesting && (added + deleted == 0))) {
                        total_files--;
                } else if (!data->files[i]->is_binary) { /* don't count bytes */
                        adds += added;
                        dels += deleted;
                }
        }
        fprintf(options->file, "%s", diff_line_prefix(options));
        print_stat_summary(options->file, total_files, adds, dels);
}

static void show_numstat(struct diffstat_t *data, struct diff_options *options)
{
        int i;

        if (data->nr == 0)
                return;

        for (i = 0; i < data->nr; i++) {
                struct diffstat_file *file = data->files[i];

                fprintf(options->file, "%s", diff_line_prefix(options));

                if (file->is_binary)
                        fprintf(options->file, "-\t-\t");
                else
                        fprintf(options->file,
                                "%"PRIuMAX"\t%"PRIuMAX"\t",
                                file->added, file->deleted);
                if (options->line_termination) {
                        fill_print_name(file);
                        if (!file->is_renamed)
                                write_name_quoted(file->name, options->file,
                                                  options->line_termination);
                        else {
                                fputs(file->print_name, options->file);
                                putc(options->line_termination, options->file);
                        }
                } else {
                        if (file->is_renamed) {
                                putc('\0', options->file);
                                write_name_quoted(file->from_name, options->file, '\0');
                        }
                        write_name_quoted(file->name, options->file, '\0');
                }
        }
}

struct dirstat_file {
        const char *name;
        unsigned long changed;
};

struct dirstat_dir {
        struct dirstat_file *files;
        int alloc, nr, permille, cumulative;
};

static long gather_dirstat(struct diff_options *opt, struct dirstat_dir *dir,
                unsigned long changed, const char *base, int baselen)
{
        unsigned long this_dir = 0;
        unsigned int sources = 0;
        const char *line_prefix = diff_line_prefix(opt);

        while (dir->nr) {
                struct dirstat_file *f = dir->files;
                int namelen = strlen(f->name);
                unsigned long this;
                char *slash;

                if (namelen < baselen)
                        break;
                if (memcmp(f->name, base, baselen))
                        break;
                slash = strchr(f->name + baselen, '/');
                if (slash) {
                        int newbaselen = slash + 1 - f->name;
                        this = gather_dirstat(opt, dir, changed, f->name, newbaselen);
                        sources++;
                } else {
                        this = f->changed;
                        dir->files++;
                        dir->nr--;
                        sources += 2;
                }
                this_dir += this;
        }

        /*
         * We don't report dirstat's for
         *  - the top level
         *  - or cases where everything came from a single directory
         *    under this directory (sources == 1).
         */
        if (baselen && sources != 1) {
                if (this_dir) {
                        int permille = this_dir * 1000 / changed;
                        if (permille >= dir->permille) {
                                fprintf(opt->file, "%s%4d.%01d%% %.*s\n", line_prefix,
                                        permille / 10, permille % 10, baselen, base);
                                if (!dir->cumulative)
                                        return 0;
                        }
                }
        }
        return this_dir;
}

static int dirstat_compare(const void *_a, const void *_b)
{
        const struct dirstat_file *a = _a;
        const struct dirstat_file *b = _b;
        return strcmp(a->name, b->name);
}

static void show_dirstat(struct diff_options *options)
{
        int i;
        unsigned long changed;
        struct dirstat_dir dir;
        struct diff_queue_struct *q = &diff_queued_diff;

        dir.files = NULL;
        dir.alloc = 0;
        dir.nr = 0;
        dir.permille = options->dirstat_permille;
        dir.cumulative = DIFF_OPT_TST(options, DIRSTAT_CUMULATIVE);

        changed = 0;
        for (i = 0; i < q->nr; i++) {
                struct diff_filepair *p = q->queue[i];
                const char *name;
                unsigned long copied, added, damage;
                int content_changed;

                name = p->two->path ? p->two->path : p->one->path;

                if (p->one->oid_valid && p->two->oid_valid)
                        content_changed = oidcmp(&p->one->oid, &p->two->oid);
                else
                        content_changed = 1;

                if (!content_changed) {
                        /*
                         * The SHA1 has not changed, so pre-/post-content is
                         * identical. We can therefore skip looking at the
                         * file contents altogether.
                         */
                        damage = 0;
                        goto found_damage;
                }

                if (DIFF_OPT_TST(options, DIRSTAT_BY_FILE)) {
                        /*
                         * In --dirstat-by-file mode, we don't really need to
                         * look at the actual file contents at all.
                         * The fact that the SHA1 changed is enough for us to
                         * add this file to the list of results
                         * (with each file contributing equal damage).
                         */
                        damage = 1;
                        goto found_damage;
                }

                if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
                        diff_populate_filespec(p->one, 0);
                        diff_populate_filespec(p->two, 0);
                        diffcore_count_changes(p->one, p->two, NULL, NULL, 0,
                                               &copied, &added);
                        diff_free_filespec_data(p->one);
                        diff_free_filespec_data(p->two);
                } else if (DIFF_FILE_VALID(p->one)) {
                        diff_populate_filespec(p->one, CHECK_SIZE_ONLY);
                        copied = added = 0;
                        diff_free_filespec_data(p->one);
                } else if (DIFF_FILE_VALID(p->two)) {
                        diff_populate_filespec(p->two, CHECK_SIZE_ONLY);
                        copied = 0;
                        added = p->two->size;
                        diff_free_filespec_data(p->two);
                } else
                        continue;

                /*
                 * Original minus copied is the removed material,
                 * added is the new material.  They are both damages
                 * made to the preimage.
                 * If the resulting damage is zero, we know that
                 * diffcore_count_changes() considers the two entries to
                 * be identical, but since content_changed is true, we
                 * know that there must have been _some_ kind of change,
                 * so we force all entries to have damage > 0.
                 */
                damage = (p->one->size - copied) + added;
                if (!damage)
                        damage = 1;

found_damage:
                ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);
                dir.files[dir.nr].name = name;
                dir.files[dir.nr].changed = damage;
                changed += damage;
                dir.nr++;
        }

        /* This can happen even with many files, if everything was renames */
        if (!changed)
                return;

        /* Show all directories with more than x% of the changes */
        qsort(dir.files, dir.nr, sizeof(dir.files[0]), dirstat_compare);
        gather_dirstat(options, &dir, changed, "", 0);
}

static void show_dirstat_by_line(struct diffstat_t *data, struct diff_options *options)
{
        int i;
        unsigned long changed;
        struct dirstat_dir dir;

        if (data->nr == 0)
                return;

        dir.files = NULL;
        dir.alloc = 0;
        dir.nr = 0;
        dir.permille = options->dirstat_permille;
        dir.cumulative = DIFF_OPT_TST(options, DIRSTAT_CUMULATIVE);

        changed = 0;
        for (i = 0; i < data->nr; i++) {
                struct diffstat_file *file = data->files[i];
                unsigned long damage = file->added + file->deleted;
                if (file->is_binary)
                        /*
                         * binary files counts bytes, not lines. Must find some
                         * way to normalize binary bytes vs. textual lines.
                         * The following heuristic assumes that there are 64
                         * bytes per "line".
                         * This is stupid and ugly, but very cheap...
                         */
                        damage = (damage + 63) / 64;
                ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);
                dir.files[dir.nr].name = file->name;
                dir.files[dir.nr].changed = damage;
                changed += damage;
                dir.nr++;
        }

        /* This can happen even with many files, if everything was renames */
        if (!changed)
                return;

        /* Show all directories with more than x% of the changes */
        qsort(dir.files, dir.nr, sizeof(dir.files[0]), dirstat_compare);
        gather_dirstat(options, &dir, changed, "", 0);
}

static void free_diffstat_info(struct diffstat_t *diffstat)
{
        int i;
        for (i = 0; i < diffstat->nr; i++) {
                struct diffstat_file *f = diffstat->files[i];
                if (f->name != f->print_name)
                        free(f->print_name);
                free(f->name);
                free(f->from_name);
                free(f);
        }
        free(diffstat->files);
}

struct checkdiff_t {
        const char *filename;
        int lineno;
        int conflict_marker_size;
        struct diff_options *o;
        unsigned ws_rule;
        unsigned status;
};

static int is_conflict_marker(const char *line, int marker_size, unsigned long len)
{
        char firstchar;
        int cnt;

        if (len < marker_size + 1)
                return 0;
        firstchar = line[0];
        switch (firstchar) {
        case '=': case '>': case '<': case '|':
                break;
        default:
                return 0;
        }
        for (cnt = 1; cnt < marker_size; cnt++)
                if (line[cnt] != firstchar)
                        return 0;
        /* line[1] thru line[marker_size-1] are same as firstchar */
        if (len < marker_size + 1 || !isspace(line[marker_size]))
                return 0;
        return 1;
}

static void checkdiff_consume(void *priv, char *line, unsigned long len)
{
        struct checkdiff_t *data = priv;
        int marker_size = data->conflict_marker_size;
        const char *ws = diff_get_color(data->o->use_color, DIFF_WHITESPACE);
        const char *reset = diff_get_color(data->o->use_color, DIFF_RESET);
        const char *set = diff_get_color(data->o->use_color, DIFF_FILE_NEW);
        char *err;
        const char *line_prefix;

        assert(data->o);
        line_prefix = diff_line_prefix(data->o);

        if (line[0] == '+') {
                unsigned bad;
                data->lineno++;
                if (is_conflict_marker(line + 1, marker_size, len - 1)) {
                        data->status |= 1;
                        fprintf(data->o->file,
                                "%s%s:%d: leftover conflict marker\n",
                                line_prefix, data->filename, data->lineno);
                }
                bad = ws_check(line + 1, len - 1, data->ws_rule);
                if (!bad)
                        return;
                data->status |= bad;
                err = whitespace_error_string(bad);
                fprintf(data->o->file, "%s%s:%d: %s.\n",
                        line_prefix, data->filename, data->lineno, err);
                free(err);
                emit_line(data->o, set, reset, line, 1);
                ws_check_emit(line + 1, len - 1, data->ws_rule,
                              data->o->file, set, reset, ws);
        } else if (line[0] == ' ') {
                data->lineno++;
        } else if (line[0] == '@') {
                char *plus = strchr(line, '+');
                if (plus)
                        data->lineno = strtol(plus, NULL, 10) - 1;
                else
                        die("invalid diff");
        }
}

static unsigned char *deflate_it(char *data,
                                 unsigned long size,
                                 unsigned long *result_size)
{
        int bound;
        unsigned char *deflated;
        git_zstream stream;

        git_deflate_init(&stream, zlib_compression_level);
        bound = git_deflate_bound(&stream, size);
        deflated = xmalloc(bound);
        stream.next_out = deflated;
        stream.avail_out = bound;

        stream.next_in = (unsigned char *)data;
        stream.avail_in = size;
        while (git_deflate(&stream, Z_FINISH) == Z_OK)
                ; /* nothing */
        git_deflate_end(&stream);
        *result_size = stream.total_out;
        return deflated;
}

static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two,
                                  const char *prefix)
{
        void *cp;
        void *delta;
        void *deflated;
        void *data;
        unsigned long orig_size;
        unsigned long delta_size;
        unsigned long deflate_size;
        unsigned long data_size;

        /* We could do deflated delta, or we could do just deflated two,
         * whichever is smaller.
         */
        delta = NULL;
        deflated = deflate_it(two->ptr, two->size, &deflate_size);
        if (one->size && two->size) {
                delta = diff_delta(one->ptr, one->size,
                                   two->ptr, two->size,
                                   &delta_size, deflate_size);
                if (delta) {
                        void *to_free = delta;
                        orig_size = delta_size;
                        delta = deflate_it(delta, delta_size, &delta_size);
                        free(to_free);
                }
        }

        if (delta && delta_size < deflate_size) {
                fprintf(file, "%sdelta %lu\n", prefix, orig_size);
                free(deflated);
                data = delta;
                data_size = delta_size;
        }
        else {
                fprintf(file, "%sliteral %lu\n", prefix, two->size);
                free(delta);
                data = deflated;
                data_size = deflate_size;
        }

        /* emit data encoded in base85 */
        cp = data;
        while (data_size) {
                int bytes = (52 < data_size) ? 52 : data_size;
                char line[70];
                data_size -= bytes;
                if (bytes <= 26)
                        line[0] = bytes + 'A' - 1;
                else
                        line[0] = bytes - 26 + 'a' - 1;
                encode_85(line + 1, cp, bytes);
                cp = (char *) cp + bytes;
                fprintf(file, "%s", prefix);
                fputs(line, file);
                fputc('\n', file);
        }
        fprintf(file, "%s\n", prefix);
        free(data);
}

static void emit_binary_diff(FILE *file, mmfile_t *one, mmfile_t *two,
                             const char *prefix)
{
        fprintf(file, "%sGIT binary patch\n", prefix);
        emit_binary_diff_body(file, one, two, prefix);
        emit_binary_diff_body(file, two, one, prefix);
}

int diff_filespec_is_binary(struct diff_filespec *one)
{
        if (one->is_binary == -1) {
                diff_filespec_load_driver(one);
                if (one->driver->binary != -1)
                        one->is_binary = one->driver->binary;
                else {
                        if (!one->data && DIFF_FILE_VALID(one))
                                diff_populate_filespec(one, CHECK_BINARY);
                        if (one->is_binary == -1 && one->data)
                                one->is_binary = buffer_is_binary(one->data,
                                                one->size);
                        if (one->is_binary == -1)
                                one->is_binary = 0;
                }
        }
        return one->is_binary;
}

static const struct userdiff_funcname *diff_funcname_pattern(struct diff_filespec *one)
{
        diff_filespec_load_driver(one);
        return one->driver->funcname.pattern ? &one->driver->funcname : NULL;
}

void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b)
{
        if (!options->a_prefix)
                options->a_prefix = a;
        if (!options->b_prefix)
                options->b_prefix = b;
}

struct userdiff_driver *get_textconv(struct diff_filespec *one)
{
        if (!DIFF_FILE_VALID(one))
                return NULL;

        diff_filespec_load_driver(one);
        return userdiff_get_textconv(one->driver);
}

static void builtin_diff(const char *name_a,
                         const char *name_b,
                         struct diff_filespec *one,
                         struct diff_filespec *two,
                         const char *xfrm_msg,
                         int must_show_header,
                         struct diff_options *o,
                         int complete_rewrite)
{
        mmfile_t mf1, mf2;
        const char *lbl[2];
        char *a_one, *b_two;
        const char *meta = diff_get_color_opt(o, DIFF_METAINFO);
        const char *reset = diff_get_color_opt(o, DIFF_RESET);
        const char *a_prefix, *b_prefix;
        struct userdiff_driver *textconv_one = NULL;
        struct userdiff_driver *textconv_two = NULL;
        struct strbuf header = STRBUF_INIT;
        const char *line_prefix = diff_line_prefix(o);

        diff_set_mnemonic_prefix(o, "a/", "b/");
        if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
                a_prefix = o->b_prefix;
                b_prefix = o->a_prefix;
        } else {
                a_prefix = o->a_prefix;
                b_prefix = o->b_prefix;
        }

        if (o->submodule_format == DIFF_SUBMODULE_LOG &&
            (!one->mode || S_ISGITLINK(one->mode)) &&
            (!two->mode || S_ISGITLINK(two->mode))) {
                const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
                const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
                show_submodule_summary(o->file, one->path ? one->path : two->path,
                                line_prefix,
                                &one->oid, &two->oid,
                                two->dirty_submodule,
                                meta, del, add, reset);
                return;
        } else if (o->submodule_format == DIFF_SUBMODULE_INLINE_DIFF &&
                   (!one->mode || S_ISGITLINK(one->mode)) &&
                   (!two->mode || S_ISGITLINK(two->mode))) {
                const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
                const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
                show_submodule_inline_diff(o->file, one->path ? one->path : two->path,
                                line_prefix,
                                &one->oid, &two->oid,
                                two->dirty_submodule,
                                meta, del, add, reset, o);
                return;
        }

        if (DIFF_OPT_TST(o, ALLOW_TEXTCONV)) {
                textconv_one = get_textconv(one);
                textconv_two = get_textconv(two);
        }

        /* Never use a non-valid filename anywhere if at all possible */
        name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
        name_b = DIFF_FILE_VALID(two) ? name_b : name_a;

        a_one = quote_two(a_prefix, name_a + (*name_a == '/'));
        b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
        lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
        lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
        strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix, meta, a_one, b_two, reset);
        if (lbl[0][0] == '/') {
                /* /dev/null */
                strbuf_addf(&header, "%s%snew file mode %06o%s\n", line_prefix, meta, two->mode, reset);
                if (xfrm_msg)
                        strbuf_addstr(&header, xfrm_msg);
                must_show_header = 1;
        }
        else if (lbl[1][0] == '/') {
                strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n", line_prefix, meta, one->mode, reset);
                if (xfrm_msg)
                        strbuf_addstr(&header, xfrm_msg);
                must_show_header = 1;
        }
        else {
                if (one->mode != two->mode) {
                        strbuf_addf(&header, "%s%sold mode %06o%s\n", line_prefix, meta, one->mode, reset);
                        strbuf_addf(&header, "%s%snew mode %06o%s\n", line_prefix, meta, two->mode, reset);
                        must_show_header = 1;
                }
                if (xfrm_msg)
                        strbuf_addstr(&header, xfrm_msg);

                /*
                 * we do not run diff between different kind
                 * of objects.
                 */
                if ((one->mode ^ two->mode) & S_IFMT)
                        goto free_ab_and_return;
                if (complete_rewrite &&
                    (textconv_one || !diff_filespec_is_binary(one)) &&
                    (textconv_two || !diff_filespec_is_binary(two))) {
                        fprintf(o->file, "%s", header.buf);
                        strbuf_reset(&header);
                        emit_rewrite_diff(name_a, name_b, one, two,
                                                textconv_one, textconv_two, o);
                        o->found_changes = 1;
                        goto free_ab_and_return;
                }
        }

        if (o->irreversible_delete && lbl[1][0] == '/') {
                fprintf(o->file, "%s", header.buf);
                strbuf_reset(&header);
                goto free_ab_and_return;
        } else if (!DIFF_OPT_TST(o, TEXT) &&
            ( (!textconv_one && diff_filespec_is_binary(one)) ||
              (!textconv_two && diff_filespec_is_binary(two)) )) {
                if (!one->data && !two->data &&
                    S_ISREG(one->mode) && S_ISREG(two->mode) &&
                    !DIFF_OPT_TST(o, BINARY)) {
                        if (!oidcmp(&one->oid, &two->oid)) {
                                if (must_show_header)
                                        fprintf(o->file, "%s", header.buf);
                                goto free_ab_and_return;
                        }
                        fprintf(o->file, "%s", header.buf);
                        fprintf(o->file, "%sBinary files %s and %s differ\n",
                                line_prefix, lbl[0], lbl[1]);
                        goto free_ab_and_return;
                }
                if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
                        die("unable to read files to diff");
                /* Quite common confusing case */
                if (mf1.size == mf2.size &&
                    !memcmp(mf1.ptr, mf2.ptr, mf1.size)) {
                        if (must_show_header)
                                fprintf(o->file, "%s", header.buf);
                        goto free_ab_and_return;
                }
                fprintf(o->file, "%s", header.buf);
                strbuf_reset(&header);
                if (DIFF_OPT_TST(o, BINARY))
                        emit_binary_diff(o->file, &mf1, &mf2, line_prefix);
                else
                        fprintf(o->file, "%sBinary files %s and %s differ\n",
                                line_prefix, lbl[0], lbl[1]);
                o->found_changes = 1;
        } else {
                /* Crazy xdl interfaces.. */
                const char *diffopts = getenv("GIT_DIFF_OPTS");
                const char *v;
                xpparam_t xpp;
                xdemitconf_t xecfg;
                struct emit_callback ecbdata;
                const struct userdiff_funcname *pe;

                if (must_show_header) {
                        fprintf(o->file, "%s", header.buf);
                        strbuf_reset(&header);
                }

                mf1.size = fill_textconv(textconv_one, one, &mf1.ptr);
                mf2.size = fill_textconv(textconv_two, two, &mf2.ptr);

                pe = diff_funcname_pattern(one);
                if (!pe)
                        pe = diff_funcname_pattern(two);

                memset(&xpp, 0, sizeof(xpp));
                memset(&xecfg, 0, sizeof(xecfg));
                memset(&ecbdata, 0, sizeof(ecbdata));
                ecbdata.label_path = lbl;
                ecbdata.color_diff = want_color(o->use_color);
                ecbdata.found_changesp = &o->found_changes;
                ecbdata.ws_rule = whitespace_rule(name_b);
                if (ecbdata.ws_rule & WS_BLANK_AT_EOF)
                        check_blank_at_eof(&mf1, &mf2, &ecbdata);
                ecbdata.opt = o;
                ecbdata.header = header.len ? &header : NULL;
                xpp.flags = o->xdl_opts;
                xecfg.ctxlen = o->context;
                xecfg.interhunkctxlen = o->interhunkcontext;
                xecfg.flags = XDL_EMIT_FUNCNAMES;
                if (DIFF_OPT_TST(o, FUNCCONTEXT))
                        xecfg.flags |= XDL_EMIT_FUNCCONTEXT;
                if (pe)
                        xdiff_set_find_func(&xecfg, pe->pattern, pe->cflags);
                if (!diffopts)
                        ;
                else if (skip_prefix(diffopts, "--unified=", &v))
                        xecfg.ctxlen = strtoul(v, NULL, 10);
                else if (skip_prefix(diffopts, "-u", &v))
                        xecfg.ctxlen = strtoul(v, NULL, 10);
                if (o->word_diff)
                        init_diff_words_data(&ecbdata, o, one, two);
                if (xdi_diff_outf(&mf1, &mf2, fn_out_consume, &ecbdata,
                                  &xpp, &xecfg))
                        die("unable to generate diff for %s", one->path);
                if (o->word_diff)
                        free_diff_words_data(&ecbdata);
                if (textconv_one)
                        free(mf1.ptr);
                if (textconv_two)
                        free(mf2.ptr);
                xdiff_clear_find_func(&xecfg);
        }

 free_ab_and_return:
        strbuf_release(&header);
        diff_free_filespec_data(one);
        diff_free_filespec_data(two);
        free(a_one);
        free(b_two);
        return;
}

static void builtin_diffstat(const char *name_a, const char *name_b,
                             struct diff_filespec *one,
                             struct diff_filespec *two,
                             struct diffstat_t *diffstat,
                             struct diff_options *o,
                             struct diff_filepair *p)
{
        mmfile_t mf1, mf2;
        struct diffstat_file *data;
        int same_contents;
        int complete_rewrite = 0;

        if (!DIFF_PAIR_UNMERGED(p)) {
                if (p->status == DIFF_STATUS_MODIFIED && p->score)
                        complete_rewrite = 1;
        }

        data = diffstat_add(diffstat, name_a, name_b);
        data->is_interesting = p->status != DIFF_STATUS_UNKNOWN;

        if (!one || !two) {
                data->is_unmerged = 1;
                return;
        }

        same_contents = !oidcmp(&one->oid, &two->oid);

        if (diff_filespec_is_binary(one) || diff_filespec_is_binary(two)) {
                data->is_binary = 1;
                if (same_contents) {
                        data->added = 0;
                        data->deleted = 0;
                } else {
                        data->added = diff_filespec_size(two);
                        data->deleted = diff_filespec_size(one);
                }
        }

        else if (complete_rewrite) {
                diff_populate_filespec(one, 0);
                diff_populate_filespec(two, 0);
                data->deleted = count_lines(one->data, one->size);
                data->added = count_lines(two->data, two->size);
        }

        else if (!same_contents) {
                /* Crazy xdl interfaces.. */
                xpparam_t xpp;
                xdemitconf_t xecfg;

                if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
                        die("unable to read files to diff");

                memset(&xpp, 0, sizeof(xpp));
                memset(&xecfg, 0, sizeof(xecfg));
                xpp.flags = o->xdl_opts;
                xecfg.ctxlen = o->context;
                xecfg.interhunkctxlen = o->interhunkcontext;
                if (xdi_diff_outf(&mf1, &mf2, diffstat_consume, diffstat,
                                  &xpp, &xecfg))
                        die("unable to generate diffstat for %s", one->path);
        }

        diff_free_filespec_data(one);
        diff_free_filespec_data(two);
}

static void builtin_checkdiff(const char *name_a, const char *name_b,
                              const char *attr_path,
                              struct diff_filespec *one,
                              struct diff_filespec *two,
                              struct diff_options *o)
{
        mmfile_t mf1, mf2;
        struct checkdiff_t data;

        if (!two)
                return;

        memset(&data, 0, sizeof(data));
        data.filename = name_b ? name_b : name_a;
        data.lineno = 0;
        data.o = o;
        data.ws_rule = whitespace_rule(attr_path);
        data.conflict_marker_size = ll_merge_marker_size(attr_path);

        if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
                die("unable to read files to diff");

        /*
         * All the other codepaths check both sides, but not checking
         * the "old" side here is deliberate.  We are checking the newly
         * introduced changes, and as long as the "new" side is text, we
         * can and should check what it introduces.
         */
        if (diff_filespec_is_binary(two))
                goto free_and_return;
        else {
                /* Crazy xdl interfaces.. */
                xpparam_t xpp;
                xdemitconf_t xecfg;

                memset(&xpp, 0, sizeof(xpp));
                memset(&xecfg, 0, sizeof(xecfg));
                xecfg.ctxlen = 1; /* at least one context line */
                xpp.flags = 0;
                if (xdi_diff_outf(&mf1, &mf2, checkdiff_consume, &data,
                                  &xpp, &xecfg))
                        die("unable to generate checkdiff for %s", one->path);

                if (data.ws_rule & WS_BLANK_AT_EOF) {
                        struct emit_callback ecbdata;
                        int blank_at_eof;

                        ecbdata.ws_rule = data.ws_rule;
                        check_blank_at_eof(&mf1, &mf2, &ecbdata);
                        blank_at_eof = ecbdata.blank_at_eof_in_postimage;

                        if (blank_at_eof) {
                                static char *err;
                                if (!err)
                                        err = whitespace_error_string(WS_BLANK_AT_EOF);
                                fprintf(o->file, "%s:%d: %s.\n",
                                        data.filename, blank_at_eof, err);
                                data.status = 1; /* report errors */
                        }
                }
        }
 free_and_return:
        diff_free_filespec_data(one);
        diff_free_filespec_data(two);
        if (data.status)
                DIFF_OPT_SET(o, CHECK_FAILED);
}

struct diff_filespec *alloc_filespec(const char *path)
{
        struct diff_filespec *spec;

        FLEXPTR_ALLOC_STR(spec, path, path);
        spec->count = 1;
        spec->is_binary = -1;
        return spec;
}

void free_filespec(struct diff_filespec *spec)
{
        if (!--spec->count) {
                diff_free_filespec_data(spec);
                free(spec);
        }
}

void fill_filespec(struct diff_filespec *spec, const unsigned char *sha1,
                   int sha1_valid, unsigned short mode)
{
        if (mode) {
                spec->mode = canon_mode(mode);
                hashcpy(spec->oid.hash, sha1);
                spec->oid_valid = sha1_valid;
        }
}

/*
 * Given a name and sha1 pair, if the index tells us the file in
 * the work tree has that object contents, return true, so that
 * prepare_temp_file() does not have to inflate and extract.
 */
static int reuse_worktree_file(const char *name, const unsigned char *sha1, int want_file)
{
        const struct cache_entry *ce;
        struct stat st;
        int pos, len;

        /*
         * We do not read the cache ourselves here, because the
         * benchmark with my previous version that always reads cache
         * shows that it makes things worse for diff-tree comparing
         * two linux-2.6 kernel trees in an already checked out work
         * tree.  This is because most diff-tree comparisons deal with
         * only a small number of files, while reading the cache is
         * expensive for a large project, and its cost outweighs the
         * savings we get by not inflating the object to a temporary
         * file.  Practically, this code only helps when we are used
         * by diff-cache --cached, which does read the cache before
         * calling us.
         */
        if (!active_cache)
                return 0;

        /* We want to avoid the working directory if our caller
         * doesn't need the data in a normal file, this system
         * is rather slow with its stat/open/mmap/close syscalls,
         * and the object is contained in a pack file.  The pack
         * is probably already open and will be faster to obtain
         * the data through than the working directory.  Loose
         * objects however would tend to be slower as they need
         * to be individually opened and inflated.
         */
        if (!FAST_WORKING_DIRECTORY && !want_file && has_sha1_pack(sha1))
                return 0;

        /*
         * Similarly, if we'd have to convert the file contents anyway, that
         * makes the optimization not worthwhile.
         */
        if (!want_file && would_convert_to_git(name))
                return 0;

        len = strlen(name);
        pos = cache_name_pos(name, len);
        if (pos < 0)
                return 0;
        ce = active_cache[pos];

        /*
         * This is not the sha1 we are looking for, or
         * unreusable because it is not a regular file.
         */
        if (hashcmp(sha1, ce->sha1) || !S_ISREG(ce->ce_mode))
                return 0;

        /*
         * If ce is marked as "assume unchanged", there is no
         * guarantee that work tree matches what we are looking for.
         */
        if ((ce->ce_flags & CE_VALID) || ce_skip_worktree(ce))
                return 0;

        /*
         * If ce matches the file in the work tree, we can reuse it.
         */
        if (ce_uptodate(ce) ||
            (!lstat(name, &st) && !ce_match_stat(ce, &st, 0)))
                return 1;

        return 0;
}

static int diff_populate_gitlink(struct diff_filespec *s, int size_only)
{
        struct strbuf buf = STRBUF_INIT;
        char *dirty = "";

        /* Are we looking at the work tree? */
        if (s->dirty_submodule)
                dirty = "-dirty";

        strbuf_addf(&buf, "Subproject commit %s%s\n",
                    oid_to_hex(&s->oid), dirty);
        s->size = buf.len;
        if (size_only) {
                s->data = NULL;
                strbuf_release(&buf);
        } else {
                s->data = strbuf_detach(&buf, NULL);
                s->should_free = 1;
        }
        return 0;
}

/*
 * While doing rename detection and pickaxe operation, we may need to
 * grab the data for the blob (or file) for our own in-core comparison.
 * diff_filespec has data and size fields for this purpose.
 */
int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
{
        int size_only = flags & CHECK_SIZE_ONLY;
        int err = 0;
        /*
         * demote FAIL to WARN to allow inspecting the situation
         * instead of refusing.
         */
        enum safe_crlf crlf_warn = (safe_crlf == SAFE_CRLF_FAIL
                                    ? SAFE_CRLF_WARN
                                    : safe_crlf);

        if (!DIFF_FILE_VALID(s))
                die("internal error: asking to populate invalid file.");
        if (S_ISDIR(s->mode))
                return -1;

        if (s->data)
                return 0;

        if (size_only && 0 < s->size)
                return 0;

        if (S_ISGITLINK(s->mode))
                return diff_populate_gitlink(s, size_only);

        if (!s->oid_valid ||
            reuse_worktree_file(s->path, s->oid.hash, 0)) {
                struct strbuf buf = STRBUF_INIT;
                struct stat st;
                int fd;

                if (lstat(s->path, &st) < 0) {
                        if (errno == ENOENT) {
                        err_empty:
                                err = -1;
                        empty:
                                s->data = (char *)"";
                                s->size = 0;
                                return err;
                        }
                }
                s->size = xsize_t(st.st_size);
                if (!s->size)
                        goto empty;
                if (S_ISLNK(st.st_mode)) {
                        struct strbuf sb = STRBUF_INIT;

                        if (strbuf_readlink(&sb, s->path, s->size))
                                goto err_empty;
                        s->size = sb.len;
                        s->data = strbuf_detach(&sb, NULL);
                        s->should_free = 1;
                        return 0;
                }
                if (size_only)
                        return 0;
                if ((flags & CHECK_BINARY) &&
                    s->size > big_file_threshold && s->is_binary == -1) {
                        s->is_binary = 1;
                        return 0;
                }
                fd = open(s->path, O_RDONLY);
                if (fd < 0)
                        goto err_empty;
                s->data = xmmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
                close(fd);
                s->should_munmap = 1;

                /*
                 * Convert from working tree format to canonical git format
                 */
                if (convert_to_git(s->path, s->data, s->size, &buf, crlf_warn)) {
                        size_t size = 0;
                        munmap(s->data, s->size);
                        s->should_munmap = 0;
                        s->data = strbuf_detach(&buf, &size);
                        s->size = size;
                        s->should_free = 1;
                }
        }
        else {
                enum object_type type;
                if (size_only || (flags & CHECK_BINARY)) {
                        type = sha1_object_info(s->oid.hash, &s->size);
                        if (type < 0)
                                die("unable to read %s",
                                    oid_to_hex(&s->oid));
                        if (size_only)
                                return 0;
                        if (s->size > big_file_threshold && s->is_binary == -1) {
                                s->is_binary = 1;
                                return 0;
                        }
                }
                s->data = read_sha1_file(s->oid.hash, &type, &s->size);
                if (!s->data)
                        die("unable to read %s", oid_to_hex(&s->oid));
                s->should_free = 1;
        }
        return 0;
}

void diff_free_filespec_blob(struct diff_filespec *s)
{
        if (s->should_free)
                free(s->data);
        else if (s->should_munmap)
                munmap(s->data, s->size);

        if (s->should_free || s->should_munmap) {
                s->should_free = s->should_munmap = 0;
                s->data = NULL;
        }
}

void diff_free_filespec_data(struct diff_filespec *s)
{
        diff_free_filespec_blob(s);
        free(s->cnt_data);
        s->cnt_data = NULL;
}

static void prep_temp_blob(const char *path, struct diff_tempfile *temp,
                           void *blob,
                           unsigned long size,
                           const struct object_id *oid,
                           int mode)
{
        int fd;
        struct strbuf buf = STRBUF_INIT;
        struct strbuf template = STRBUF_INIT;
        char *path_dup = xstrdup(path);
        const char *base = basename(path_dup);

        /* Generate "XXXXXX_basename.ext" */
        strbuf_addstr(&template, "XXXXXX_");
        strbuf_addstr(&template, base);

        fd = mks_tempfile_ts(&temp->tempfile, template.buf, strlen(base) + 1);
        if (fd < 0)
                die_errno("unable to create temp-file");
        if (convert_to_working_tree(path,
                        (const char *)blob, (size_t)size, &buf)) {
                blob = buf.buf;
                size = buf.len;
        }
        if (write_in_full(fd, blob, size) != size)
                die_errno("unable to write temp-file");
        close_tempfile(&temp->tempfile);
        temp->name = get_tempfile_path(&temp->tempfile);
        oid_to_hex_r(temp->hex, oid);
        xsnprintf(temp->mode, sizeof(temp->mode), "%06o", mode);
        strbuf_release(&buf);
        strbuf_release(&template);
        free(path_dup);
}

static struct diff_tempfile *prepare_temp_file(const char *name,
                struct diff_filespec *one)
{
        struct diff_tempfile *temp = claim_diff_tempfile();

        if (!DIFF_FILE_VALID(one)) {
        not_a_valid_file:
                /* A '-' entry produces this for file-2, and
                 * a '+' entry produces this for file-1.
                 */
                temp->name = "/dev/null";
                xsnprintf(temp->hex, sizeof(temp->hex), ".");
                xsnprintf(temp->mode, sizeof(temp->mode), ".");
                return temp;
        }

        if (!S_ISGITLINK(one->mode) &&
            (!one->oid_valid ||
             reuse_worktree_file(name, one->oid.hash, 1))) {
                struct stat st;
                if (lstat(name, &st) < 0) {
                        if (errno == ENOENT)
                                goto not_a_valid_file;
                        die_errno("stat(%s)", name);
                }
                if (S_ISLNK(st.st_mode)) {
                        struct strbuf sb = STRBUF_INIT;
                        if (strbuf_readlink(&sb, name, st.st_size) < 0)
                                die_errno("readlink(%s)", name);
                        prep_temp_blob(name, temp, sb.buf, sb.len,
                                       (one->oid_valid ?
                                        &one->oid : &null_oid),
                                       (one->oid_valid ?
                                        one->mode : S_IFLNK));
                        strbuf_release(&sb);
                }
                else {
                        /* we can borrow from the file in the work tree */
                        temp->name = name;
                        if (!one->oid_valid)
                                sha1_to_hex_r(temp->hex, null_sha1);
                        else
                                sha1_to_hex_r(temp->hex, one->oid.hash);
                        /* Even though we may sometimes borrow the
                         * contents from the work tree, we always want
                         * one->mode.  mode is trustworthy even when
                         * !(one->sha1_valid), as long as
                         * DIFF_FILE_VALID(one).
                         */
                        xsnprintf(temp->mode, sizeof(temp->mode), "%06o", one->mode);
                }
                return temp;
        }
        else {
                if (diff_populate_filespec(one, 0))
                        die("cannot read data blob for %s", one->path);
                prep_temp_blob(name, temp, one->data, one->size,
                               &one->oid, one->mode);
        }
        return temp;
}

static void add_external_diff_name(struct argv_array *argv,
                                   const char *name,
                                   struct diff_filespec *df)
{
        struct diff_tempfile *temp = prepare_temp_file(name, df);
        argv_array_push(argv, temp->name);
        argv_array_push(argv, temp->hex);
        argv_array_push(argv, temp->mode);
}

/* An external diff command takes:
 *
 * diff-cmd name infile1 infile1-sha1 infile1-mode \
 *               infile2 infile2-sha1 infile2-mode [ rename-to ]
 *
 */
static void run_external_diff(const char *pgm,
                              const char *name,
                              const char *other,
                              struct diff_filespec *one,
                              struct diff_filespec *two,
                              const char *xfrm_msg,
                              int complete_rewrite,
                              struct diff_options *o)
{
        struct argv_array argv = ARGV_ARRAY_INIT;
        struct argv_array env = ARGV_ARRAY_INIT;
        struct diff_queue_struct *q = &diff_queued_diff;

        argv_array_push(&argv, pgm);
        argv_array_push(&argv, name);

        if (one && two) {
                add_external_diff_name(&argv, name, one);
                if (!other)
                        add_external_diff_name(&argv, name, two);
                else {
                        add_external_diff_name(&argv, other, two);
                        argv_array_push(&argv, other);
                        argv_array_push(&argv, xfrm_msg);
                }
        }

        argv_array_pushf(&env, "GIT_DIFF_PATH_COUNTER=%d", ++o->diff_path_counter);
        argv_array_pushf(&env, "GIT_DIFF_PATH_TOTAL=%d", q->nr);

        if (run_command_v_opt_cd_env(argv.argv, RUN_USING_SHELL, NULL, env.argv))
                die(_("external diff died, stopping at %s"), name);

        remove_tempfile();
        argv_array_clear(&argv);
        argv_array_clear(&env);
}

static int similarity_index(struct diff_filepair *p)
{
        return p->score * 100 / MAX_SCORE;
}

static void fill_metainfo(struct strbuf *msg,
                          const char *name,
                          const char *other,
                          struct diff_filespec *one,
                          struct diff_filespec *two,
                          struct diff_options *o,
                          struct diff_filepair *p,
                          int *must_show_header,
                          int use_color)
{
        const char *set = diff_get_color(use_color, DIFF_METAINFO);
        const char *reset = diff_get_color(use_color, DIFF_RESET);
        const char *line_prefix = diff_line_prefix(o);

        *must_show_header = 1;
        strbuf_init(msg, PATH_MAX * 2 + 300);
        switch (p->status) {
        case DIFF_STATUS_COPIED:
                strbuf_addf(msg, "%s%ssimilarity index %d%%",
                            line_prefix, set, similarity_index(p));
                strbuf_addf(msg, "%s\n%s%scopy from ",
                            reset,  line_prefix, set);
                quote_c_style(name, msg, NULL, 0);
                strbuf_addf(msg, "%s\n%s%scopy to ", reset, line_prefix, set);
                quote_c_style(other, msg, NULL, 0);
                strbuf_addf(msg, "%s\n", reset);
                break;
        case DIFF_STATUS_RENAMED:
                strbuf_addf(msg, "%s%ssimilarity index %d%%",
                            line_prefix, set, similarity_index(p));
                strbuf_addf(msg, "%s\n%s%srename from ",
                            reset, line_prefix, set);
                quote_c_style(name, msg, NULL, 0);
                strbuf_addf(msg, "%s\n%s%srename to ",
                            reset, line_prefix, set);
                quote_c_style(other, msg, NULL, 0);
                strbuf_addf(msg, "%s\n", reset);
                break;
        case DIFF_STATUS_MODIFIED:
                if (p->score) {
                        strbuf_addf(msg, "%s%sdissimilarity index %d%%%s\n",
                                    line_prefix,
                                    set, similarity_index(p), reset);
                        break;
                }
                /* fallthru */
        default:
                *must_show_header = 0;
        }
        if (one && two && oidcmp(&one->oid, &two->oid)) {
                int abbrev = DIFF_OPT_TST(o, FULL_INDEX) ? 40 : DEFAULT_ABBREV;

                if (DIFF_OPT_TST(o, BINARY)) {
                        mmfile_t mf;
                        if ((!fill_mmfile(&mf, one) && diff_filespec_is_binary(one)) ||
                            (!fill_mmfile(&mf, two) && diff_filespec_is_binary(two)))
                                abbrev = 40;
                }
                strbuf_addf(msg, "%s%sindex %s..", line_prefix, set,
                            find_unique_abbrev(one->oid.hash, abbrev));
                strbuf_addstr(msg, find_unique_abbrev(two->oid.hash, abbrev));
                if (one->mode == two->mode)
                        strbuf_addf(msg, " %06o", one->mode);
                strbuf_addf(msg, "%s\n", reset);
        }
}

static void run_diff_cmd(const char *pgm,
                         const char *name,
                         const char *other,
                         const char *attr_path,
                         struct diff_filespec *one,
                         struct diff_filespec *two,
                         struct strbuf *msg,
                         struct diff_options *o,
                         struct diff_filepair *p)
{
        const char *xfrm_msg = NULL;
        int complete_rewrite = (p->status == DIFF_STATUS_MODIFIED) && p->score;
        int must_show_header = 0;


        if (DIFF_OPT_TST(o, ALLOW_EXTERNAL)) {
                struct userdiff_driver *drv = userdiff_find_by_path(attr_path);
                if (drv && drv->external)
                        pgm = drv->external;
        }

        if (msg) {
                /*
                 * don't use colors when the header is intended for an
                 * external diff driver
                 */
                fill_metainfo(msg, name, other, one, two, o, p,
                              &must_show_header,
                              want_color(o->use_color) && !pgm);
                xfrm_msg = msg->len ? msg->buf : NULL;
        }

        if (pgm) {
                run_external_diff(pgm, name, other, one, two, xfrm_msg,
                                  complete_rewrite, o);
                return;
        }
        if (one && two)
                builtin_diff(name, other ? other : name,
                             one, two, xfrm_msg, must_show_header,
                             o, complete_rewrite);
        else
                fprintf(o->file, "* Unmerged path %s\n", name);
}

static void diff_fill_sha1_info(struct diff_filespec *one)
{
        if (DIFF_FILE_VALID(one)) {
                if (!one->oid_valid) {
                        struct stat st;
                        if (one->is_stdin) {
                                oidclr(&one->oid);
                                return;
                        }
                        if (lstat(one->path, &st) < 0)
                                die_errno("stat '%s'", one->path);
                        if (index_path(one->oid.hash, one->path, &st, 0))
                                die("cannot hash %s", one->path);
                }
        }
        else
                oidclr(&one->oid);
}

static void strip_prefix(int prefix_length, const char **namep, const char **otherp)
{
        /* Strip the prefix but do not molest /dev/null and absolute paths */
        if (*namep && **namep != '/') {
                *namep += prefix_length;
                if (**namep == '/')
                        ++*namep;
        }
        if (*otherp && **otherp != '/') {
                *otherp += prefix_length;
                if (**otherp == '/')
                        ++*otherp;
        }
}

static void run_diff(struct diff_filepair *p, struct diff_options *o)
{
        const char *pgm = external_diff();
        struct strbuf msg;
        struct diff_filespec *one = p->one;
        struct diff_filespec *two = p->two;
        const char *name;
        const char *other;
        const char *attr_path;

        name  = p->one->path;
        other = (strcmp(name, p->two->path) ? p->two->path : NULL);
        attr_path = name;
        if (o->prefix_length)
                strip_prefix(o->prefix_length, &name, &other);

        if (!DIFF_OPT_TST(o, ALLOW_EXTERNAL))
                pgm = NULL;

        if (DIFF_PAIR_UNMERGED(p)) {
                run_diff_cmd(pgm, name, NULL, attr_path,
                             NULL, NULL, NULL, o, p);
                return;
        }

        diff_fill_sha1_info(one);
        diff_fill_sha1_info(two);

        if (!pgm &&
            DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two) &&
            (S_IFMT & one->mode) != (S_IFMT & two->mode)) {
                /*
                 * a filepair that changes between file and symlink
                 * needs to be split into deletion and creation.
                 */
                struct diff_filespec *null = alloc_filespec(two->path);
                run_diff_cmd(NULL, name, other, attr_path,
                             one, null, &msg, o, p);
                free(null);
                strbuf_release(&msg);

                null = alloc_filespec(one->path);
                run_diff_cmd(NULL, name, other, attr_path,
                             null, two, &msg, o, p);
                free(null);
        }
        else
                run_diff_cmd(pgm, name, other, attr_path,
                             one, two, &msg, o, p);

        strbuf_release(&msg);
}

static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
                         struct diffstat_t *diffstat)
{
        const char *name;
        const char *other;

        if (DIFF_PAIR_UNMERGED(p)) {
                /* unmerged */
                builtin_diffstat(p->one->path, NULL, NULL, NULL, diffstat, o, p);
                return;
        }

        name = p->one->path;
        other = (strcmp(name, p->two->path) ? p->two->path : NULL);

        if (o->prefix_length)
                strip_prefix(o->prefix_length, &name, &other);

        diff_fill_sha1_info(p->one);
        diff_fill_sha1_info(p->two);

        builtin_diffstat(name, other, p->one, p->two, diffstat, o, p);
}

static void run_checkdiff(struct diff_filepair *p, struct diff_options *o)
{
        const char *name;
        const char *other;
        const char *attr_path;

        if (DIFF_PAIR_UNMERGED(p)) {
                /* unmerged */
                return;
        }

        name = p->one->path;
        other = (strcmp(name, p->two->path) ? p->two->path : NULL);
        attr_path = other ? other : name;

        if (o->prefix_length)
                strip_prefix(o->prefix_length, &name, &other);

        diff_fill_sha1_info(p->one);
        diff_fill_sha1_info(p->two);

        builtin_checkdiff(name, other, attr_path, p->one, p->two, o);
}

void diff_setup(struct diff_options *options)
{
        memcpy(options, &default_diff_options, sizeof(*options));

        options->file = stdout;

        options->line_termination = '\n';
        options->break_opt = -1;
        options->rename_limit = -1;
        options->dirstat_permille = diff_dirstat_permille_default;
        options->context = diff_context_default;
        options->ws_error_highlight = WSEH_NEW;
        DIFF_OPT_SET(options, RENAME_EMPTY);

        /* pathchange left =NULL by default */
        options->change = diff_change;
        options->add_remove = diff_addremove;
        options->use_color = diff_use_color_default;
        options->detect_rename = diff_detect_rename_default;
        options->xdl_opts |= diff_algorithm;
        if (diff_compaction_heuristic)
                DIFF_XDL_SET(options, COMPACTION_HEURISTIC);

        options->orderfile = diff_order_file_cfg;

        if (diff_no_prefix) {
                options->a_prefix = options->b_prefix = "";
        } else if (!diff_mnemonic_prefix) {
                options->a_prefix = "a/";
                options->b_prefix = "b/";
        }
}

void diff_setup_done(struct diff_options *options)
{
        int count = 0;

        if (options->set_default)
                options->set_default(options);

        if (options->output_format & DIFF_FORMAT_NAME)
                count++;
        if (options->output_format & DIFF_FORMAT_NAME_STATUS)
                count++;
        if (options->output_format & DIFF_FORMAT_CHECKDIFF)
                count++;
        if (options->output_format & DIFF_FORMAT_NO_OUTPUT)
                count++;
        if (count > 1)
                die("--name-only, --name-status, --check and -s are mutually exclusive");

        /*
         * Most of the time we can say "there are changes"
         * only by checking if there are changed paths, but
         * --ignore-whitespace* options force us to look
         * inside contents.
         */

        if (DIFF_XDL_TST(options, IGNORE_WHITESPACE) ||
            DIFF_XDL_TST(options, IGNORE_WHITESPACE_CHANGE) ||
            DIFF_XDL_TST(options, IGNORE_WHITESPACE_AT_EOL))
                DIFF_OPT_SET(options, DIFF_FROM_CONTENTS);
        else
                DIFF_OPT_CLR(options, DIFF_FROM_CONTENTS);

        if (DIFF_OPT_TST(options, FIND_COPIES_HARDER))
                options->detect_rename = DIFF_DETECT_COPY;

        if (!DIFF_OPT_TST(options, RELATIVE_NAME))
                options->prefix = NULL;
        if (options->prefix)
                options->prefix_length = strlen(options->prefix);
        else
                options->prefix_length = 0;

        if (options->output_format & (DIFF_FORMAT_NAME |
                                      DIFF_FORMAT_NAME_STATUS |
                                      DIFF_FORMAT_CHECKDIFF |
                                      DIFF_FORMAT_NO_OUTPUT))
                options->output_format &= ~(DIFF_FORMAT_RAW |
                                            DIFF_FORMAT_NUMSTAT |
                                            DIFF_FORMAT_DIFFSTAT |
                                            DIFF_FORMAT_SHORTSTAT |
                                            DIFF_FORMAT_DIRSTAT |
                                            DIFF_FORMAT_SUMMARY |
                                            DIFF_FORMAT_PATCH);

        /*
         * These cases always need recursive; we do not drop caller-supplied
         * recursive bits for other formats here.
         */
        if (options->output_format & (DIFF_FORMAT_PATCH |
                                      DIFF_FORMAT_NUMSTAT |
                                      DIFF_FORMAT_DIFFSTAT |
                                      DIFF_FORMAT_SHORTSTAT |
                                      DIFF_FORMAT_DIRSTAT |
                                      DIFF_FORMAT_SUMMARY |
                                      DIFF_FORMAT_CHECKDIFF))
                DIFF_OPT_SET(options, RECURSIVE);
        /*
         * Also pickaxe would not work very well if you do not say recursive
         */
        if (options->pickaxe)
                DIFF_OPT_SET(options, RECURSIVE);
        /*
         * When patches are generated, submodules diffed against the work tree
         * must be checked for dirtiness too so it can be shown in the output
         */
        if (options->output_format & DIFF_FORMAT_PATCH)
                DIFF_OPT_SET(options, DIRTY_SUBMODULES);

        if (options->detect_rename && options->rename_limit < 0)
                options->rename_limit = diff_rename_limit_default;
        if (options->setup & DIFF_SETUP_USE_CACHE) {
                if (!active_cache)
                        /* read-cache does not die even when it fails
                         * so it is safe for us to do this here.  Also
                         * it does not smudge active_cache or active_nr
                         * when it fails, so we do not have to worry about
                         * cleaning it up ourselves either.
                         */
                        read_cache();
        }
        if (options->abbrev <= 0 || 40 < options->abbrev)
                options->abbrev = 40; /* full */

        /*
         * It does not make sense to show the first hit we happened
         * to have found.  It does not make sense not to return with
         * exit code in such a case either.
         */
        if (DIFF_OPT_TST(options, QUICK)) {
                options->output_format = DIFF_FORMAT_NO_OUTPUT;
                DIFF_OPT_SET(options, EXIT_WITH_STATUS);
        }

        options->diff_path_counter = 0;

        if (DIFF_OPT_TST(options, FOLLOW_RENAMES) && options->pathspec.nr != 1)
                die(_("--follow requires exactly one pathspec"));
}

static int opt_arg(const char *arg, int arg_short, const char *arg_long, int *val)
{
        char c, *eq;
        int len;

        if (*arg != '-')
                return 0;
        c = *++arg;
        if (!c)
                return 0;
        if (c == arg_short) {
                c = *++arg;
                if (!c)
                        return 1;
                if (val && isdigit(c)) {
                        char *end;
                        int n = strtoul(arg, &end, 10);
                        if (*end)
                                return 0;
                        *val = n;
                        return 1;
                }
                return 0;
        }
        if (c != '-')
                return 0;
        arg++;
        eq = strchrnul(arg, '=');
        len = eq - arg;
        if (!len || strncmp(arg, arg_long, len))
                return 0;
        if (*eq) {
                int n;
                char *end;
                if (!isdigit(*++eq))
                        return 0;
                n = strtoul(eq, &end, 10);
                if (*end)
                        return 0;
                *val = n;
        }
        return 1;
}

static int diff_scoreopt_parse(const char *opt);

static inline int short_opt(char opt, const char **argv,
                            const char **optarg)
{
        const char *arg = argv[0];
        if (arg[0] != '-' || arg[1] != opt)
                return 0;
        if (arg[2] != '\0') {
                *optarg = arg + 2;
                return 1;
        }
        if (!argv[1])
                die("Option '%c' requires a value", opt);
        *optarg = argv[1];
        return 2;
}

int parse_long_opt(const char *opt, const char **argv,
                   const char **optarg)
{
        const char *arg = argv[0];
        if (!skip_prefix(arg, "--", &arg))
                return 0;
        if (!skip_prefix(arg, opt, &arg))
                return 0;
        if (*arg == '=') { /* stuck form: --option=value */
                *optarg = arg + 1;
                return 1;
        }
        if (*arg != '\0')
                return 0;
        /* separate form: --option value */
        if (!argv[1])
                die("Option '--%s' requires a value", opt);
        *optarg = argv[1];
        return 2;
}

static int stat_opt(struct diff_options *options, const char **av)
{
        const char *arg = av[0];
        char *end;
        int width = options->stat_width;
        int name_width = options->stat_name_width;
        int graph_width = options->stat_graph_width;
        int count = options->stat_count;
        int argcount = 1;

        if (!skip_prefix(arg, "--stat", &arg))
                die("BUG: stat option does not begin with --stat: %s", arg);
        end = (char *)arg;

        switch (*arg) {
        case '-':
                if (skip_prefix(arg, "-width", &arg)) {
                        if (*arg == '=')
                                width = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
                                die("Option '--stat-width' requires a value");
                        else if (!*arg) {
                                width = strtoul(av[1], &end, 10);
                                argcount = 2;
                        }
                } else if (skip_prefix(arg, "-name-width", &arg)) {
                        if (*arg == '=')
                                name_width = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
                                die("Option '--stat-name-width' requires a value");
                        else if (!*arg) {
                                name_width = strtoul(av[1], &end, 10);
                                argcount = 2;
                        }
                } else if (skip_prefix(arg, "-graph-width", &arg)) {
                        if (*arg == '=')
                                graph_width = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
                                die("Option '--stat-graph-width' requires a value");
                        else if (!*arg) {
                                graph_width = strtoul(av[1], &end, 10);
                                argcount = 2;
                        }
                } else if (skip_prefix(arg, "-count", &arg)) {
                        if (*arg == '=')
                                count = strtoul(arg + 1, &end, 10);
                        else if (!*arg && !av[1])
                                die("Option '--stat-count' requires a value");
                        else if (!*arg) {
                                count = strtoul(av[1], &end, 10);
                                argcount = 2;
                        }
                }
                break;
        case '=':
                width = strtoul(arg+1, &end, 10);
                if (*end == ',')
                        name_width = strtoul(end+1, &end, 10);
                if (*end == ',')
                        count = strtoul(end+1, &end, 10);
        }

        /* Important! This checks all the error cases! */
        if (*end)
                return 0;
        options->output_format |= DIFF_FORMAT_DIFFSTAT;
        options->stat_name_width = name_width;
        options->stat_graph_width = graph_width;
        options->stat_width = width;
        options->stat_count = count;
        return argcount;
}

static int parse_dirstat_opt(struct diff_options *options, const char *params)
{
        struct strbuf errmsg = STRBUF_INIT;
        if (parse_dirstat_params(options, params, &errmsg))
                die(_("Failed to parse --dirstat/-X option parameter:\n%s"),
                    errmsg.buf);
        strbuf_release(&errmsg);
        /*
         * The caller knows a dirstat-related option is given from the command
         * line; allow it to say "return this_function();"
         */
        options->output_format |= DIFF_FORMAT_DIRSTAT;
        return 1;
}

static int parse_submodule_opt(struct diff_options *options, const char *value)
{
        if (parse_submodule_params(options, value))
                die(_("Failed to parse --submodule option parameter: '%s'"),
                        value);
        return 1;
}

static const char diff_status_letters[] = {
        DIFF_STATUS_ADDED,
        DIFF_STATUS_COPIED,
        DIFF_STATUS_DELETED,
        DIFF_STATUS_MODIFIED,
        DIFF_STATUS_RENAMED,
        DIFF_STATUS_TYPE_CHANGED,
        DIFF_STATUS_UNKNOWN,
        DIFF_STATUS_UNMERGED,
        DIFF_STATUS_FILTER_AON,
        DIFF_STATUS_FILTER_BROKEN,
        '\0',
};

static unsigned int filter_bit['Z' + 1];

static void prepare_filter_bits(void)
{
        int i;

        if (!filter_bit[DIFF_STATUS_ADDED]) {
                for (i = 0; diff_status_letters[i]; i++)
                        filter_bit[(int) diff_status_letters[i]] = (1 << i);
        }
}

static unsigned filter_bit_tst(char status, const struct diff_options *opt)
{
        return opt->filter & filter_bit[(int) status];
}

static int parse_diff_filter_opt(const char *optarg, struct diff_options *opt)
{
        int i, optch;

        prepare_filter_bits();

        /*
         * If there is a negation e.g. 'd' in the input, and we haven't
         * initialized the filter field with another --diff-filter, start
         * from full set of bits, except for AON.
         */
        if (!opt->filter) {
                for (i = 0; (optch = optarg[i]) != '\0'; i++) {
                        if (optch < 'a' || 'z' < optch)
                                continue;
                        opt->filter = (1 << (ARRAY_SIZE(diff_status_letters) - 1)) - 1;
                        opt->filter &= ~filter_bit[DIFF_STATUS_FILTER_AON];
                        break;
                }
        }

        for (i = 0; (optch = optarg[i]) != '\0'; i++) {
                unsigned int bit;
                int negate;

                if ('a' <= optch && optch <= 'z') {
                        negate = 1;
                        optch = toupper(optch);
                } else {
                        negate = 0;
                }

                bit = (0 <= optch && optch <= 'Z') ? filter_bit[optch] : 0;
                if (!bit)
                        return optarg[i];
                if (negate)
                        opt->filter &= ~bit;
                else
                        opt->filter |= bit;
        }
        return 0;
}

static void enable_patch_output(int *fmt) {
        *fmt &= ~DIFF_FORMAT_NO_OUTPUT;
        *fmt |= DIFF_FORMAT_PATCH;
}

static int parse_one_token(const char **arg, const char *token)
{
        const char *rest;
        if (skip_prefix(*arg, token, &rest) && (!*rest || *rest == ',')) {
                *arg = rest;
                return 1;
        }
        return 0;
}

static int parse_ws_error_highlight(struct diff_options *opt, const char *arg)
{
        const char *orig_arg = arg;
        unsigned val = 0;
        while (*arg) {
                if (parse_one_token(&arg, "none"))
                        val = 0;
                else if (parse_one_token(&arg, "default"))
                        val = WSEH_NEW;
                else if (parse_one_token(&arg, "all"))
                        val = WSEH_NEW | WSEH_OLD | WSEH_CONTEXT;
                else if (parse_one_token(&arg, "new"))
                        val |= WSEH_NEW;
                else if (parse_one_token(&arg, "old"))
                        val |= WSEH_OLD;
                else if (parse_one_token(&arg, "context"))
                        val |= WSEH_CONTEXT;
                else {
                        error("unknown value after ws-error-highlight=%.*s",
                              (int)(arg - orig_arg), orig_arg);
                        return 0;
                }
                if (*arg)
                        arg++;
        }
        opt->ws_error_highlight = val;
        return 1;
}

int diff_opt_parse(struct diff_options *options,
                   const char **av, int ac, const char *prefix)
{
        const char *arg = av[0];
        const char *optarg;
        int argcount;

        if (!prefix)
                prefix = "";

        /* Output format options */
        if (!strcmp(arg, "-p") || !strcmp(arg, "-u") || !strcmp(arg, "--patch")
            || opt_arg(arg, 'U', "unified", &options->context))
                enable_patch_output(&options->output_format);
        else if (!strcmp(arg, "--raw"))
                options->output_format |= DIFF_FORMAT_RAW;
        else if (!strcmp(arg, "--patch-with-raw")) {
                enable_patch_output(&options->output_format);
                options->output_format |= DIFF_FORMAT_RAW;
        } else if (!strcmp(arg, "--numstat"))
                options->output_format |= DIFF_FORMAT_NUMSTAT;
        else if (!strcmp(arg, "--shortstat"))
                options->output_format |= DIFF_FORMAT_SHORTSTAT;
        else if (!strcmp(arg, "-X") || !strcmp(arg, "--dirstat"))
                return parse_dirstat_opt(options, "");
        else if (skip_prefix(arg, "-X", &arg))
                return parse_dirstat_opt(options, arg);
        else if (skip_prefix(arg, "--dirstat=", &arg))
                return parse_dirstat_opt(options, arg);
        else if (!strcmp(arg, "--cumulative"))
                return parse_dirstat_opt(options, "cumulative");
        else if (!strcmp(arg, "--dirstat-by-file"))
                return parse_dirstat_opt(options, "files");
        else if (skip_prefix(arg, "--dirstat-by-file=", &arg)) {
                parse_dirstat_opt(options, "files");
                return parse_dirstat_opt(options, arg);
        }
        else if (!strcmp(arg, "--check"))
                options->output_format |= DIFF_FORMAT_CHECKDIFF;
        else if (!strcmp(arg, "--summary"))
                options->output_format |= DIFF_FORMAT_SUMMARY;
        else if (!strcmp(arg, "--patch-with-stat")) {
                enable_patch_output(&options->output_format);
                options->output_format |= DIFF_FORMAT_DIFFSTAT;
        } else if (!strcmp(arg, "--name-only"))
                options->output_format |= DIFF_FORMAT_NAME;
        else if (!strcmp(arg, "--name-status"))
                options->output_format |= DIFF_FORMAT_NAME_STATUS;
        else if (!strcmp(arg, "-s") || !strcmp(arg, "--no-patch"))
                options->output_format |= DIFF_FORMAT_NO_OUTPUT;
        else if (starts_with(arg, "--stat"))
                /* --stat, --stat-width, --stat-name-width, or --stat-count */
                return stat_opt(options, av);

        /* renames options */
        else if (starts_with(arg, "-B") || starts_with(arg, "--break-rewrites=") ||
                 !strcmp(arg, "--break-rewrites")) {
                if ((options->break_opt = diff_scoreopt_parse(arg)) == -1)
                        return error("invalid argument to -B: %s", arg+2);
        }
        else if (starts_with(arg, "-M") || starts_with(arg, "--find-renames=") ||
                 !strcmp(arg, "--find-renames")) {
                if ((options->rename_score = diff_scoreopt_parse(arg)) == -1)
                        return error("invalid argument to -M: %s", arg+2);
                options->detect_rename = DIFF_DETECT_RENAME;
        }
        else if (!strcmp(arg, "-D") || !strcmp(arg, "--irreversible-delete")) {
                options->irreversible_delete = 1;
        }
        else if (starts_with(arg, "-C") || starts_with(arg, "--find-copies=") ||
                 !strcmp(arg, "--find-copies")) {
                if (options->detect_rename == DIFF_DETECT_COPY)
                        DIFF_OPT_SET(options, FIND_COPIES_HARDER);
                if ((options->rename_score = diff_scoreopt_parse(arg)) == -1)
                        return error("invalid argument to -C: %s", arg+2);
                options->detect_rename = DIFF_DETECT_COPY;
        }
        else if (!strcmp(arg, "--no-renames"))
                options->detect_rename = 0;
        else if (!strcmp(arg, "--rename-empty"))
                DIFF_OPT_SET(options, RENAME_EMPTY);
        else if (!strcmp(arg, "--no-rename-empty"))
                DIFF_OPT_CLR(options, RENAME_EMPTY);
        else if (!strcmp(arg, "--relative"))
                DIFF_OPT_SET(options, RELATIVE_NAME);
        else if (skip_prefix(arg, "--relative=", &arg)) {
                DIFF_OPT_SET(options, RELATIVE_NAME);
                options->prefix = arg;
        }

        /* xdiff options */
        else if (!strcmp(arg, "--minimal"))
                DIFF_XDL_SET(options, NEED_MINIMAL);
        else if (!strcmp(arg, "--no-minimal"))
                DIFF_XDL_CLR(options, NEED_MINIMAL);
        else if (!strcmp(arg, "-w") || !strcmp(arg, "--ignore-all-space"))
                DIFF_XDL_SET(options, IGNORE_WHITESPACE);
        else if (!strcmp(arg, "-b") || !strcmp(arg, "--ignore-space-change"))
                DIFF_XDL_SET(options, IGNORE_WHITESPACE_CHANGE);
        else if (!strcmp(arg, "--ignore-space-at-eol"))
                DIFF_XDL_SET(options, IGNORE_WHITESPACE_AT_EOL);
        else if (!strcmp(arg, "--ignore-blank-lines"))
                DIFF_XDL_SET(options, IGNORE_BLANK_LINES);
        else if (!strcmp(arg, "--compaction-heuristic"))
                DIFF_XDL_SET(options, COMPACTION_HEURISTIC);
        else if (!strcmp(arg, "--no-compaction-heuristic"))
                DIFF_XDL_CLR(options, COMPACTION_HEURISTIC);
        else if (!strcmp(arg, "--patience"))
                options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
        else if (!strcmp(arg, "--histogram"))
                options->xdl_opts = DIFF_WITH_ALG(options, HISTOGRAM_DIFF);
        else if ((argcount = parse_long_opt("diff-algorithm", av, &optarg))) {
                long value = parse_algorithm_value(optarg);
                if (value < 0)
                        return error("option diff-algorithm accepts \"myers\", "
                                     "\"minimal\", \"patience\" and \"histogram\"");
                /* clear out previous settings */
                DIFF_XDL_CLR(options, NEED_MINIMAL);
                options->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
                options->xdl_opts |= value;
                return argcount;
        }

        /* flags options */
        else if (!strcmp(arg, "--binary")) {
                enable_patch_output(&options->output_format);
                DIFF_OPT_SET(options, BINARY);
        }
        else if (!strcmp(arg, "--full-index"))
                DIFF_OPT_SET(options, FULL_INDEX);
        else if (!strcmp(arg, "-a") || !strcmp(arg, "--text"))
                DIFF_OPT_SET(options, TEXT);
        else if (!strcmp(arg, "-R"))
                DIFF_OPT_SET(options, REVERSE_DIFF);
        else if (!strcmp(arg, "--find-copies-harder"))
                DIFF_OPT_SET(options, FIND_COPIES_HARDER);
        else if (!strcmp(arg, "--follow"))
                DIFF_OPT_SET(options, FOLLOW_RENAMES);
        else if (!strcmp(arg, "--no-follow")) {
                DIFF_OPT_CLR(options, FOLLOW_RENAMES);
                DIFF_OPT_CLR(options, DEFAULT_FOLLOW_RENAMES);
        } else if (!strcmp(arg, "--color"))
                options->use_color = 1;
        else if (skip_prefix(arg, "--color=", &arg)) {
                int value = git_config_colorbool(NULL, arg);
                if (value < 0)
                        return error("option `color' expects \"always\", \"auto\", or \"never\"");
                options->use_color = value;
        }
        else if (!strcmp(arg, "--no-color"))
                options->use_color = 0;
        else if (!strcmp(arg, "--color-words")) {
                options->use_color = 1;
                options->word_diff = DIFF_WORDS_COLOR;
        }
        else if (skip_prefix(arg, "--color-words=", &arg)) {
                options->use_color = 1;
                options->word_diff = DIFF_WORDS_COLOR;
                options->word_regex = arg;
        }
        else if (!strcmp(arg, "--word-diff")) {
                if (options->word_diff == DIFF_WORDS_NONE)
                        options->word_diff = DIFF_WORDS_PLAIN;
        }
        else if (skip_prefix(arg, "--word-diff=", &arg)) {
                if (!strcmp(arg, "plain"))
                        options->word_diff = DIFF_WORDS_PLAIN;
                else if (!strcmp(arg, "color")) {
                        options->use_color = 1;
                        options->word_diff = DIFF_WORDS_COLOR;
                }
                else if (!strcmp(arg, "porcelain"))
                        options->word_diff = DIFF_WORDS_PORCELAIN;
                else if (!strcmp(arg, "none"))
                        options->word_diff = DIFF_WORDS_NONE;
                else
                        die("bad --word-diff argument: %s", arg);
        }
        else if ((argcount = parse_long_opt("word-diff-regex", av, &optarg))) {
                if (options->word_diff == DIFF_WORDS_NONE)
                        options->word_diff = DIFF_WORDS_PLAIN;
                options->word_regex = optarg;
                return argcount;
        }
        else if (!strcmp(arg, "--exit-code"))
                DIFF_OPT_SET(options, EXIT_WITH_STATUS);
        else if (!strcmp(arg, "--quiet"))
                DIFF_OPT_SET(options, QUICK);
        else if (!strcmp(arg, "--ext-diff"))
                DIFF_OPT_SET(options, ALLOW_EXTERNAL);
        else if (!strcmp(arg, "--no-ext-diff"))
                DIFF_OPT_CLR(options, ALLOW_EXTERNAL);
        else if (!strcmp(arg, "--textconv"))
                DIFF_OPT_SET(options, ALLOW_TEXTCONV);
        else if (!strcmp(arg, "--no-textconv"))
                DIFF_OPT_CLR(options, ALLOW_TEXTCONV);
        else if (!strcmp(arg, "--ignore-submodules")) {
                DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
                handle_ignore_submodules_arg(options, "all");
        } else if (skip_prefix(arg, "--ignore-submodules=", &arg)) {
                DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
                handle_ignore_submodules_arg(options, arg);
        } else if (!strcmp(arg, "--submodule"))
                options->submodule_format = DIFF_SUBMODULE_LOG;
        else if (skip_prefix(arg, "--submodule=", &arg))
                return parse_submodule_opt(options, arg);
        else if (skip_prefix(arg, "--ws-error-highlight=", &arg))
                return parse_ws_error_highlight(options, arg);

        /* misc options */
        else if (!strcmp(arg, "-z"))
                options->line_termination = 0;
        else if ((argcount = short_opt('l', av, &optarg))) {
                options->rename_limit = strtoul(optarg, NULL, 10);
                return argcount;
        }
        else if ((argcount = short_opt('S', av, &optarg))) {
                options->pickaxe = optarg;
                options->pickaxe_opts |= DIFF_PICKAXE_KIND_S;
                return argcount;
        } else if ((argcount = short_opt('G', av, &optarg))) {
                options->pickaxe = optarg;
                options->pickaxe_opts |= DIFF_PICKAXE_KIND_G;
                return argcount;
        }
        else if (!strcmp(arg, "--pickaxe-all"))
                options->pickaxe_opts |= DIFF_PICKAXE_ALL;
        else if (!strcmp(arg, "--pickaxe-regex"))
                options->pickaxe_opts |= DIFF_PICKAXE_REGEX;
        else if ((argcount = short_opt('O', av, &optarg))) {
                const char *path = prefix_filename(prefix, strlen(prefix), optarg);
                options->orderfile = xstrdup(path);
                return argcount;
        }
        else if ((argcount = parse_long_opt("diff-filter", av, &optarg))) {
                int offending = parse_diff_filter_opt(optarg, options);
                if (offending)
                        die("unknown change class '%c' in --diff-filter=%s",
                            offending, optarg);
                return argcount;
        }
        else if (!strcmp(arg, "--abbrev"))
                options->abbrev = DEFAULT_ABBREV;
        else if (skip_prefix(arg, "--abbrev=", &arg)) {
                options->abbrev = strtoul(arg, NULL, 10);
                if (options->abbrev < MINIMUM_ABBREV)
                        options->abbrev = MINIMUM_ABBREV;
                else if (40 < options->abbrev)
                        options->abbrev = 40;
        }
        else if ((argcount = parse_long_opt("src-prefix", av, &optarg))) {
                options->a_prefix = optarg;
                return argcount;
        }
        else if ((argcount = parse_long_opt("line-prefix", av, &optarg))) {
                options->line_prefix = optarg;
                options->line_prefix_length = strlen(options->line_prefix);
                graph_setup_line_prefix(options);
                return argcount;
        }
        else if ((argcount = parse_long_opt("dst-prefix", av, &optarg))) {
                options->b_prefix = optarg;
                return argcount;
        }
        else if (!strcmp(arg, "--no-prefix"))
                options->a_prefix = options->b_prefix = "";
        else if (opt_arg(arg, '\0', "inter-hunk-context",
                         &options->interhunkcontext))
                ;
        else if (!strcmp(arg, "-W"))
                DIFF_OPT_SET(options, FUNCCONTEXT);
        else if (!strcmp(arg, "--function-context"))
                DIFF_OPT_SET(options, FUNCCONTEXT);
        else if (!strcmp(arg, "--no-function-context"))
                DIFF_OPT_CLR(options, FUNCCONTEXT);
        else if ((argcount = parse_long_opt("output", av, &optarg))) {
                const char *path = prefix_filename(prefix, strlen(prefix), optarg);
                options->file = fopen(path, "w");
                if (!options->file)
                        die_errno("Could not open '%s'", path);
                options->close_file = 1;
                if (options->use_color != GIT_COLOR_ALWAYS)
                        options->use_color = GIT_COLOR_NEVER;
                return argcount;
        } else
                return 0;
        return 1;
}

int parse_rename_score(const char **cp_p)
{
        unsigned long num, scale;
        int ch, dot;
        const char *cp = *cp_p;

        num = 0;
        scale = 1;
        dot = 0;
        for (;;) {
                ch = *cp;
                if ( !dot && ch == '.' ) {
                        scale = 1;
                        dot = 1;
                } else if ( ch == '%' ) {
                        scale = dot ? scale*100 : 100;
                        cp++;   /* % is always at the end */
                        break;
                } else if ( ch >= '0' && ch <= '9' ) {
                        if ( scale < 100000 ) {
                                scale *= 10;
                                num = (num*10) + (ch-'0');
                        }
                } else {
                        break;
                }
                cp++;
        }
        *cp_p = cp;

        /* user says num divided by scale and we say internally that
         * is MAX_SCORE * num / scale.
         */
        return (int)((num >= scale) ? MAX_SCORE : (MAX_SCORE * num / scale));
}

static int diff_scoreopt_parse(const char *opt)
{
        int opt1, opt2, cmd;

        if (*opt++ != '-')
                return -1;
        cmd = *opt++;
        if (cmd == '-') {
                /* convert the long-form arguments into short-form versions */
                if (skip_prefix(opt, "break-rewrites", &opt)) {
                        if (*opt == 0 || *opt++ == '=')
                                cmd = 'B';
                } else if (skip_prefix(opt, "find-copies", &opt)) {
                        if (*opt == 0 || *opt++ == '=')
                                cmd = 'C';
                } else if (skip_prefix(opt, "find-renames", &opt)) {
                        if (*opt == 0 || *opt++ == '=')
                                cmd = 'M';
                }
        }
        if (cmd != 'M' && cmd != 'C' && cmd != 'B')
                return -1; /* that is not a -M, -C, or -B option */

        opt1 = parse_rename_score(&opt);
        if (cmd != 'B')
                opt2 = 0;
        else {
                if (*opt == 0)
                        opt2 = 0;
                else if (*opt != '/')
                        return -1; /* we expect -B80/99 or -B80 */
                else {
                        opt++;
                        opt2 = parse_rename_score(&opt);
                }
        }
        if (*opt != 0)
                return -1;
        return opt1 | (opt2 << 16);
}

struct diff_queue_struct diff_queued_diff;

void diff_q(struct diff_queue_struct *queue, struct diff_filepair *dp)
{
        ALLOC_GROW(queue->queue, queue->nr + 1, queue->alloc);
        queue->queue[queue->nr++] = dp;
}

struct diff_filepair *diff_queue(struct diff_queue_struct *queue,
                                 struct diff_filespec *one,
                                 struct diff_filespec *two)
{
        struct diff_filepair *dp = xcalloc(1, sizeof(*dp));
        dp->one = one;
        dp->two = two;
        if (queue)
                diff_q(queue, dp);
        return dp;
}

void diff_free_filepair(struct diff_filepair *p)
{
        free_filespec(p->one);
        free_filespec(p->two);
        free(p);
}

/* This is different from find_unique_abbrev() in that
 * it stuffs the result with dots for alignment.
 */
const char *diff_unique_abbrev(const unsigned char *sha1, int len)
{
        int abblen;
        const char *abbrev;
        if (len == 40)
                return sha1_to_hex(sha1);

        abbrev = find_unique_abbrev(sha1, len);
        abblen = strlen(abbrev);
        if (abblen < 37) {
                static char hex[41];
                if (len < abblen && abblen <= len + 2)
                        xsnprintf(hex, sizeof(hex), "%s%.*s", abbrev, len+3-abblen, "..");
                else
                        xsnprintf(hex, sizeof(hex), "%s...", abbrev);
                return hex;
        }
        return sha1_to_hex(sha1);
}

static void diff_flush_raw(struct diff_filepair *p, struct diff_options *opt)
{
        int line_termination = opt->line_termination;
        int inter_name_termination = line_termination ? '\t' : '\0';

        fprintf(opt->file, "%s", diff_line_prefix(opt));
        if (!(opt->output_format & DIFF_FORMAT_NAME_STATUS)) {
                fprintf(opt->file, ":%06o %06o %s ", p->one->mode, p->two->mode,
                        diff_unique_abbrev(p->one->oid.hash, opt->abbrev));
                fprintf(opt->file, "%s ",
                        diff_unique_abbrev(p->two->oid.hash, opt->abbrev));
        }
        if (p->score) {
                fprintf(opt->file, "%c%03d%c", p->status, similarity_index(p),
                        inter_name_termination);
        } else {
                fprintf(opt->file, "%c%c", p->status, inter_name_termination);
        }

        if (p->status == DIFF_STATUS_COPIED ||
            p->status == DIFF_STATUS_RENAMED) {
                const char *name_a, *name_b;
                name_a = p->one->path;
                name_b = p->two->path;
                strip_prefix(opt->prefix_length, &name_a, &name_b);
                write_name_quoted(name_a, opt->file, inter_name_termination);
                write_name_quoted(name_b, opt->file, line_termination);
        } else {
                const char *name_a, *name_b;
                name_a = p->one->mode ? p->one->path : p->two->path;
                name_b = NULL;
                strip_prefix(opt->prefix_length, &name_a, &name_b);
                write_name_quoted(name_a, opt->file, line_termination);
        }
}

int diff_unmodified_pair(struct diff_filepair *p)
{
        /* This function is written stricter than necessary to support
         * the currently implemented transformers, but the idea is to
         * let transformers to produce diff_filepairs any way they want,
         * and filter and clean them up here before producing the output.
         */
        struct diff_filespec *one = p->one, *two = p->two;

        if (DIFF_PAIR_UNMERGED(p))
                return 0; /* unmerged is interesting */

        /* deletion, addition, mode or type change
         * and rename are all interesting.
         */
        if (DIFF_FILE_VALID(one) != DIFF_FILE_VALID(two) ||
            DIFF_PAIR_MODE_CHANGED(p) ||
            strcmp(one->path, two->path))
                return 0;

        /* both are valid and point at the same path.  that is, we are
         * dealing with a change.
         */
        if (one->oid_valid && two->oid_valid &&
            !oidcmp(&one->oid, &two->oid) &&
            !one->dirty_submodule && !two->dirty_submodule)
                return 1; /* no change */
        if (!one->oid_valid && !two->oid_valid)
                return 1; /* both look at the same file on the filesystem. */
        return 0;
}

static void diff_flush_patch(struct diff_filepair *p, struct diff_options *o)
{
        if (diff_unmodified_pair(p))
                return;

        if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
            (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
                return; /* no tree diffs in patch format */

        run_diff(p, o);
}

static void diff_flush_stat(struct diff_filepair *p, struct diff_options *o,
                            struct diffstat_t *diffstat)
{
        if (diff_unmodified_pair(p))
                return;

        if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
            (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
                return; /* no useful stat for tree diffs */

        run_diffstat(p, o, diffstat);
}

static void diff_flush_checkdiff(struct diff_filepair *p,
                struct diff_options *o)
{
        if (diff_unmodified_pair(p))
                return;

        if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
            (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
                return; /* nothing to check in tree diffs */

        run_checkdiff(p, o);
}

int diff_queue_is_empty(void)
{
        struct diff_queue_struct *q = &diff_queued_diff;
        int i;
        for (i = 0; i < q->nr; i++)
                if (!diff_unmodified_pair(q->queue[i]))
                        return 0;
        return 1;
}

#if DIFF_DEBUG
void diff_debug_filespec(struct diff_filespec *s, int x, const char *one)
{
        fprintf(stderr, "queue[%d] %s (%s) %s %06o %s\n",
                x, one ? one : "",
                s->path,
                DIFF_FILE_VALID(s) ? "valid" : "invalid",
                s->mode,
                s->oid_valid ? oid_to_hex(&s->oid) : "");
        fprintf(stderr, "queue[%d] %s size %lu\n",
                x, one ? one : "",
                s->size);
}

void diff_debug_filepair(const struct diff_filepair *p, int i)
{
        diff_debug_filespec(p->one, i, "one");
        diff_debug_filespec(p->two, i, "two");
        fprintf(stderr, "score %d, status %c rename_used %d broken %d\n",
                p->score, p->status ? p->status : '?',
                p->one->rename_used, p->broken_pair);
}

void diff_debug_queue(const char *msg, struct diff_queue_struct *q)
{
        int i;
        if (msg)
                fprintf(stderr, "%s\n", msg);
        fprintf(stderr, "q->nr = %d\n", q->nr);
        for (i = 0; i < q->nr; i++) {
                struct diff_filepair *p = q->queue[i];
                diff_debug_filepair(p, i);
        }
}
#endif

static void diff_resolve_rename_copy(void)
{
        int i;
        struct diff_filepair *p;
        struct diff_queue_struct *q = &diff_queued_diff;

        diff_debug_queue("resolve-rename-copy", q);

        for (i = 0; i < q->nr; i++) {
                p = q->queue[i];
                p->status = 0; /* undecided */
                if (DIFF_PAIR_UNMERGED(p))
                        p->status = DIFF_STATUS_UNMERGED;
                else if (!DIFF_FILE_VALID(p->one))
                        p->status = DIFF_STATUS_ADDED;
                else if (!DIFF_FILE_VALID(p->two))
                        p->status = DIFF_STATUS_DELETED;
                else if (DIFF_PAIR_TYPE_CHANGED(p))
                        p->status = DIFF_STATUS_TYPE_CHANGED;

                /* from this point on, we are dealing with a pair
                 * whose both sides are valid and of the same type, i.e.
                 * either in-place edit or rename/copy edit.
                 */
                else if (DIFF_PAIR_RENAME(p)) {
                        /*
                         * A rename might have re-connected a broken
                         * pair up, causing the pathnames to be the
                         * same again. If so, that's not a rename at
                         * all, just a modification..
                         *
                         * Otherwise, see if this source was used for
                         * multiple renames, in which case we decrement
                         * the count, and call it a copy.
                         */
                        if (!strcmp(p->one->path, p->two->path))
                                p->status = DIFF_STATUS_MODIFIED;
                        else if (--p->one->rename_used > 0)
                                p->status = DIFF_STATUS_COPIED;
                        else
                                p->status = DIFF_STATUS_RENAMED;
                }
                else if (oidcmp(&p->one->oid, &p->two->oid) ||
                         p->one->mode != p->two->mode ||
                         p->one->dirty_submodule ||
                         p->two->dirty_submodule ||
                         is_null_oid(&p->one->oid))
                        p->status = DIFF_STATUS_MODIFIED;
                else {
                        /* This is a "no-change" entry and should not
                         * happen anymore, but prepare for broken callers.
                         */
                        error("feeding unmodified %s to diffcore",
                              p->one->path);
                        p->status = DIFF_STATUS_UNKNOWN;
                }
        }
        diff_debug_queue("resolve-rename-copy done", q);
}

static int check_pair_status(struct diff_filepair *p)
{
        switch (p->status) {
        case DIFF_STATUS_UNKNOWN:
                return 0;
        case 0:
                die("internal error in diff-resolve-rename-copy");
        default:
                return 1;
        }
}

static void flush_one_pair(struct diff_filepair *p, struct diff_options *opt)
{
        int fmt = opt->output_format;

        if (fmt & DIFF_FORMAT_CHECKDIFF)
                diff_flush_checkdiff(p, opt);
        else if (fmt & (DIFF_FORMAT_RAW | DIFF_FORMAT_NAME_STATUS))
                diff_flush_raw(p, opt);
        else if (fmt & DIFF_FORMAT_NAME) {
                const char *name_a, *name_b;
                name_a = p->two->path;
                name_b = NULL;
                strip_prefix(opt->prefix_length, &name_a, &name_b);
                write_name_quoted(name_a, opt->file, opt->line_termination);
        }
}

static void show_file_mode_name(FILE *file, const char *newdelete, struct diff_filespec *fs)
{
        if (fs->mode)
                fprintf(file, " %s mode %06o ", newdelete, fs->mode);
        else
                fprintf(file, " %s ", newdelete);
        write_name_quoted(fs->path, file, '\n');
}


static void show_mode_change(FILE *file, struct diff_filepair *p, int show_name,
                const char *line_prefix)
{
        if (p->one->mode && p->two->mode && p->one->mode != p->two->mode) {
                fprintf(file, "%s mode change %06o => %06o%c", line_prefix, p->one->mode,
                        p->two->mode, show_name ? ' ' : '\n');
                if (show_name) {
                        write_name_quoted(p->two->path, file, '\n');
                }
        }
}

static void show_rename_copy(FILE *file, const char *renamecopy, struct diff_filepair *p,
                        const char *line_prefix)
{
        char *names = pprint_rename(p->one->path, p->two->path);

        fprintf(file, " %s %s (%d%%)\n", renamecopy, names, similarity_index(p));
        free(names);
        show_mode_change(file, p, 0, line_prefix);
}

static void diff_summary(struct diff_options *opt, struct diff_filepair *p)
{
        FILE *file = opt->file;
        const char *line_prefix = diff_line_prefix(opt);

        switch(p->status) {
        case DIFF_STATUS_DELETED:
                fputs(line_prefix, file);
                show_file_mode_name(file, "delete", p->one);
                break;
        case DIFF_STATUS_ADDED:
                fputs(line_prefix, file);
                show_file_mode_name(file, "create", p->two);
                break;
        case DIFF_STATUS_COPIED:
                fputs(line_prefix, file);
                show_rename_copy(file, "copy", p, line_prefix);
                break;
        case DIFF_STATUS_RENAMED:
                fputs(line_prefix, file);
                show_rename_copy(file, "rename", p, line_prefix);
                break;
        default:
                if (p->score) {
                        fprintf(file, "%s rewrite ", line_prefix);
                        write_name_quoted(p->two->path, file, ' ');
                        fprintf(file, "(%d%%)\n", similarity_index(p));
                }
                show_mode_change(file, p, !p->score, line_prefix);
                break;
        }
}

struct patch_id_t {
        git_SHA_CTX *ctx;
        int patchlen;
};

static int remove_space(char *line, int len)
{
        int i;
        char *dst = line;
        unsigned char c;

        for (i = 0; i < len; i++)
                if (!isspace((c = line[i])))
                        *dst++ = c;

        return dst - line;
}

static void patch_id_consume(void *priv, char *line, unsigned long len)
{
        struct patch_id_t *data = priv;
        int new_len;

        /* Ignore line numbers when computing the SHA1 of the patch */
        if (starts_with(line, "@@ -"))
                return;

        new_len = remove_space(line, len);

        git_SHA1_Update(data->ctx, line, new_len);
        data->patchlen += new_len;
}

/* returns 0 upon success, and writes result into sha1 */
static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1, int diff_header_only)
{
        struct diff_queue_struct *q = &diff_queued_diff;
        int i;
        git_SHA_CTX ctx;
        struct patch_id_t data;
        char buffer[PATH_MAX * 4 + 20];

        git_SHA1_Init(&ctx);
        memset(&data, 0, sizeof(struct patch_id_t));
        data.ctx = &ctx;

        for (i = 0; i < q->nr; i++) {
                xpparam_t xpp;
                xdemitconf_t xecfg;
                mmfile_t mf1, mf2;
                struct diff_filepair *p = q->queue[i];
                int len1, len2;

                memset(&xpp, 0, sizeof(xpp));
                memset(&xecfg, 0, sizeof(xecfg));
                if (p->status == 0)
                        return error("internal diff status error");
                if (p->status == DIFF_STATUS_UNKNOWN)
                        continue;
                if (diff_unmodified_pair(p))
                        continue;
                if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
                    (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
                        continue;
                if (DIFF_PAIR_UNMERGED(p))
                        continue;

                diff_fill_sha1_info(p->one);
                diff_fill_sha1_info(p->two);

                len1 = remove_space(p->one->path, strlen(p->one->path));
                len2 = remove_space(p->two->path, strlen(p->two->path));
                if (p->one->mode == 0)
                        len1 = snprintf(buffer, sizeof(buffer),
                                        "diff--gita/%.*sb/%.*s"
                                        "newfilemode%06o"
                                        "---/dev/null"
                                        "+++b/%.*s",
                                        len1, p->one->path,
                                        len2, p->two->path,
                                        p->two->mode,
                                        len2, p->two->path);
                else if (p->two->mode == 0)
                        len1 = snprintf(buffer, sizeof(buffer),
                                        "diff--gita/%.*sb/%.*s"
                                        "deletedfilemode%06o"
                                        "---a/%.*s"
                                        "+++/dev/null",
                                        len1, p->one->path,
                                        len2, p->two->path,
                                        p->one->mode,
                                        len1, p->one->path);
                else
                        len1 = snprintf(buffer, sizeof(buffer),
                                        "diff--gita/%.*sb/%.*s"
                                        "---a/%.*s"
                                        "+++b/%.*s",
                                        len1, p->one->path,
                                        len2, p->two->path,
                                        len1, p->one->path,
                                        len2, p->two->path);
                git_SHA1_Update(&ctx, buffer, len1);

                if (diff_header_only)
                        continue;

                if (fill_mmfile(&mf1, p->one) < 0 ||
                    fill_mmfile(&mf2, p->two) < 0)
                        return error("unable to read files to diff");

                if (diff_filespec_is_binary(p->one) ||
                    diff_filespec_is_binary(p->two)) {
                        git_SHA1_Update(&ctx, oid_to_hex(&p->one->oid),
                                        40);
                        git_SHA1_Update(&ctx, oid_to_hex(&p->two->oid),
                                        40);
                        continue;
                }

                xpp.flags = 0;
                xecfg.ctxlen = 3;
                xecfg.flags = 0;
                if (xdi_diff_outf(&mf1, &mf2, patch_id_consume, &data,
                                  &xpp, &xecfg))
                        return error("unable to generate patch-id diff for %s",
                                     p->one->path);
        }

        git_SHA1_Final(sha1, &ctx);
        return 0;
}

int diff_flush_patch_id(struct diff_options *options, unsigned char *sha1, int diff_header_only)
{
        struct diff_queue_struct *q = &diff_queued_diff;
        int i;
        int result = diff_get_patch_id(options, sha1, diff_header_only);

        for (i = 0; i < q->nr; i++)
                diff_free_filepair(q->queue[i]);

        free(q->queue);
        DIFF_QUEUE_CLEAR(q);

        return result;
}

static int is_summary_empty(const struct diff_queue_struct *q)
{
        int i;

        for (i = 0; i < q->nr; i++) {
                const struct diff_filepair *p = q->queue[i];

                switch (p->status) {
                case DIFF_STATUS_DELETED:
                case DIFF_STATUS_ADDED:
                case DIFF_STATUS_COPIED:
                case DIFF_STATUS_RENAMED:
                        return 0;
                default:
                        if (p->score)
                                return 0;
                        if (p->one->mode && p->two->mode &&
                            p->one->mode != p->two->mode)
                                return 0;
                        break;
                }
        }
        return 1;
}

static const char rename_limit_warning[] =
"inexact rename detection was skipped due to too many files.";

static const char degrade_cc_to_c_warning[] =
"only found copies from modified paths due to too many files.";

static const char rename_limit_advice[] =
"you may want to set your %s variable to at least "
"%d and retry the command.";

void diff_warn_rename_limit(const char *varname, int needed, int degraded_cc)
{
        if (degraded_cc)
                warning(degrade_cc_to_c_warning);
        else if (needed)
                warning(rename_limit_warning);
        else
                return;
        if (0 < needed && needed < 32767)
                warning(rename_limit_advice, varname, needed);
}

void diff_flush(struct diff_options *options)
{
        struct diff_queue_struct *q = &diff_queued_diff;
        int i, output_format = options->output_format;
        int separator = 0;
        int dirstat_by_line = 0;

        /*
         * Order: raw, stat, summary, patch
         * or:    name/name-status/checkdiff (other bits clear)
         */
        if (!q->nr)
                goto free_queue;

        if (output_format & (DIFF_FORMAT_RAW |
                             DIFF_FORMAT_NAME |
                             DIFF_FORMAT_NAME_STATUS |
                             DIFF_FORMAT_CHECKDIFF)) {
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (check_pair_status(p))
                                flush_one_pair(p, options);
                }
                separator++;
        }

        if (output_format & DIFF_FORMAT_DIRSTAT && DIFF_OPT_TST(options, DIRSTAT_BY_LINE))
                dirstat_by_line = 1;

        if (output_format & (DIFF_FORMAT_DIFFSTAT|DIFF_FORMAT_SHORTSTAT|DIFF_FORMAT_NUMSTAT) ||
            dirstat_by_line) {
                struct diffstat_t diffstat;

                memset(&diffstat, 0, sizeof(struct diffstat_t));
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (check_pair_status(p))
                                diff_flush_stat(p, options, &diffstat);
                }
                if (output_format & DIFF_FORMAT_NUMSTAT)
                        show_numstat(&diffstat, options);
                if (output_format & DIFF_FORMAT_DIFFSTAT)
                        show_stats(&diffstat, options);
                if (output_format & DIFF_FORMAT_SHORTSTAT)
                        show_shortstats(&diffstat, options);
                if (output_format & DIFF_FORMAT_DIRSTAT && dirstat_by_line)
                        show_dirstat_by_line(&diffstat, options);
                free_diffstat_info(&diffstat);
                separator++;
        }
        if ((output_format & DIFF_FORMAT_DIRSTAT) && !dirstat_by_line)
                show_dirstat(options);

        if (output_format & DIFF_FORMAT_SUMMARY && !is_summary_empty(q)) {
                for (i = 0; i < q->nr; i++) {
                        diff_summary(options, q->queue[i]);
                }
                separator++;
        }

        if (output_format & DIFF_FORMAT_NO_OUTPUT &&
            DIFF_OPT_TST(options, EXIT_WITH_STATUS) &&
            DIFF_OPT_TST(options, DIFF_FROM_CONTENTS)) {
                /*
                 * run diff_flush_patch for the exit status. setting
                 * options->file to /dev/null should be safe, because we
                 * aren't supposed to produce any output anyway.
                 */
                if (options->close_file)
                        fclose(options->file);
                options->file = fopen("/dev/null", "w");
                if (!options->file)
                        die_errno("Could not open /dev/null");
                options->close_file = 1;
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (check_pair_status(p))
                                diff_flush_patch(p, options);
                        if (options->found_changes)
                                break;
                }
        }

        if (output_format & DIFF_FORMAT_PATCH) {
                if (separator) {
                        fprintf(options->file, "%s%c",
                                diff_line_prefix(options),
                                options->line_termination);
                        if (options->stat_sep) {
                                /* attach patch instead of inline */
                                fputs(options->stat_sep, options->file);
                        }
                }

                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (check_pair_status(p))
                                diff_flush_patch(p, options);
                }
        }

        if (output_format & DIFF_FORMAT_CALLBACK)
                options->format_callback(q, options, options->format_callback_data);

        for (i = 0; i < q->nr; i++)
                diff_free_filepair(q->queue[i]);
free_queue:
        free(q->queue);
        DIFF_QUEUE_CLEAR(q);
        if (options->close_file)
                fclose(options->file);

        /*
         * Report the content-level differences with HAS_CHANGES;
         * diff_addremove/diff_change does not set the bit when
         * DIFF_FROM_CONTENTS is in effect (e.g. with -w).
         */
        if (DIFF_OPT_TST(options, DIFF_FROM_CONTENTS)) {
                if (options->found_changes)
                        DIFF_OPT_SET(options, HAS_CHANGES);
                else
                        DIFF_OPT_CLR(options, HAS_CHANGES);
        }
}

static int match_filter(const struct diff_options *options, const struct diff_filepair *p)
{
        return (((p->status == DIFF_STATUS_MODIFIED) &&
                 ((p->score &&
                   filter_bit_tst(DIFF_STATUS_FILTER_BROKEN, options)) ||
                  (!p->score &&
                   filter_bit_tst(DIFF_STATUS_MODIFIED, options)))) ||
                ((p->status != DIFF_STATUS_MODIFIED) &&
                 filter_bit_tst(p->status, options)));
}

static void diffcore_apply_filter(struct diff_options *options)
{
        int i;
        struct diff_queue_struct *q = &diff_queued_diff;
        struct diff_queue_struct outq;

        DIFF_QUEUE_CLEAR(&outq);

        if (!options->filter)
                return;

        if (filter_bit_tst(DIFF_STATUS_FILTER_AON, options)) {
                int found;
                for (i = found = 0; !found && i < q->nr; i++) {
                        if (match_filter(options, q->queue[i]))
                                found++;
                }
                if (found)
                        return;

                /* otherwise we will clear the whole queue
                 * by copying the empty outq at the end of this
                 * function, but first clear the current entries
                 * in the queue.
                 */
                for (i = 0; i < q->nr; i++)
                        diff_free_filepair(q->queue[i]);
        }
        else {
                /* Only the matching ones */
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (match_filter(options, p))
                                diff_q(&outq, p);
                        else
                                diff_free_filepair(p);
                }
        }
        free(q->queue);
        *q = outq;
}

/* Check whether two filespecs with the same mode and size are identical */
static int diff_filespec_is_identical(struct diff_filespec *one,
                                      struct diff_filespec *two)
{
        if (S_ISGITLINK(one->mode))
                return 0;
        if (diff_populate_filespec(one, 0))
                return 0;
        if (diff_populate_filespec(two, 0))
                return 0;
        return !memcmp(one->data, two->data, one->size);
}

static int diff_filespec_check_stat_unmatch(struct diff_filepair *p)
{
        if (p->done_skip_stat_unmatch)
                return p->skip_stat_unmatch_result;

        p->done_skip_stat_unmatch = 1;
        p->skip_stat_unmatch_result = 0;
        /*
         * 1. Entries that come from stat info dirtiness
         *    always have both sides (iow, not create/delete),
         *    one side of the object name is unknown, with
         *    the same mode and size.  Keep the ones that
         *    do not match these criteria.  They have real
         *    differences.
         *
         * 2. At this point, the file is known to be modified,
         *    with the same mode and size, and the object
         *    name of one side is unknown.  Need to inspect
         *    the identical contents.
         */
        if (!DIFF_FILE_VALID(p->one) || /* (1) */
            !DIFF_FILE_VALID(p->two) ||
            (p->one->oid_valid && p->two->oid_valid) ||
            (p->one->mode != p->two->mode) ||
            diff_populate_filespec(p->one, CHECK_SIZE_ONLY) ||
            diff_populate_filespec(p->two, CHECK_SIZE_ONLY) ||
            (p->one->size != p->two->size) ||
            !diff_filespec_is_identical(p->one, p->two)) /* (2) */
                p->skip_stat_unmatch_result = 1;
        return p->skip_stat_unmatch_result;
}

static void diffcore_skip_stat_unmatch(struct diff_options *diffopt)
{
        int i;
        struct diff_queue_struct *q = &diff_queued_diff;
        struct diff_queue_struct outq;
        DIFF_QUEUE_CLEAR(&outq);

        for (i = 0; i < q->nr; i++) {
                struct diff_filepair *p = q->queue[i];

                if (diff_filespec_check_stat_unmatch(p))
                        diff_q(&outq, p);
                else {
                        /*
                         * The caller can subtract 1 from skip_stat_unmatch
                         * to determine how many paths were dirty only
                         * due to stat info mismatch.
                         */
                        if (!DIFF_OPT_TST(diffopt, NO_INDEX))
                                diffopt->skip_stat_unmatch++;
                        diff_free_filepair(p);
                }
        }
        free(q->queue);
        *q = outq;
}

static int diffnamecmp(const void *a_, const void *b_)
{
        const struct diff_filepair *a = *((const struct diff_filepair **)a_);
        const struct diff_filepair *b = *((const struct diff_filepair **)b_);
        const char *name_a, *name_b;

        name_a = a->one ? a->one->path : a->two->path;
        name_b = b->one ? b->one->path : b->two->path;
        return strcmp(name_a, name_b);
}

void diffcore_fix_diff_index(struct diff_options *options)
{
        struct diff_queue_struct *q = &diff_queued_diff;
        qsort(q->queue, q->nr, sizeof(q->queue[0]), diffnamecmp);
}

void diffcore_std(struct diff_options *options)
{
        /* NOTE please keep the following in sync with diff_tree_combined() */
        if (options->skip_stat_unmatch)
                diffcore_skip_stat_unmatch(options);
        if (!options->found_follow) {
                /* See try_to_follow_renames() in tree-diff.c */
                if (options->break_opt != -1)
                        diffcore_break(options->break_opt);
                if (options->detect_rename)
                        diffcore_rename(options);
                if (options->break_opt != -1)
                        diffcore_merge_broken();
        }
        if (options->pickaxe)
                diffcore_pickaxe(options);
        if (options->orderfile)
                diffcore_order(options->orderfile);
        if (!options->found_follow)
                /* See try_to_follow_renames() in tree-diff.c */
                diff_resolve_rename_copy();
        diffcore_apply_filter(options);

        if (diff_queued_diff.nr && !DIFF_OPT_TST(options, DIFF_FROM_CONTENTS))
                DIFF_OPT_SET(options, HAS_CHANGES);
        else
                DIFF_OPT_CLR(options, HAS_CHANGES);

        options->found_follow = 0;
}

int diff_result_code(struct diff_options *opt, int status)
{
        int result = 0;

        diff_warn_rename_limit("diff.renameLimit",
                               opt->needed_rename_limit,
                               opt->degraded_cc_to_c);
        if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
            !(opt->output_format & DIFF_FORMAT_CHECKDIFF))
                return status;
        if (DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
            DIFF_OPT_TST(opt, HAS_CHANGES))
                result |= 01;
        if ((opt->output_format & DIFF_FORMAT_CHECKDIFF) &&
            DIFF_OPT_TST(opt, CHECK_FAILED))
                result |= 02;
        return result;
}

int diff_can_quit_early(struct diff_options *opt)
{
        return (DIFF_OPT_TST(opt, QUICK) &&
                !opt->filter &&
                DIFF_OPT_TST(opt, HAS_CHANGES));
}

/*
 * Shall changes to this submodule be ignored?
 *
 * Submodule changes can be configured to be ignored separately for each path,
 * but that configuration can be overridden from the command line.
 */
static int is_submodule_ignored(const char *path, struct diff_options *options)
{
        int ignored = 0;
        unsigned orig_flags = options->flags;
        if (!DIFF_OPT_TST(options, OVERRIDE_SUBMODULE_CONFIG))
                set_diffopt_flags_from_submodule_config(options, path);
        if (DIFF_OPT_TST(options, IGNORE_SUBMODULES))
                ignored = 1;
        options->flags = orig_flags;
        return ignored;
}

void diff_addremove(struct diff_options *options,
                    int addremove, unsigned mode,
                    const unsigned char *sha1,
                    int sha1_valid,
                    const char *concatpath, unsigned dirty_submodule)
{
        struct diff_filespec *one, *two;

        if (S_ISGITLINK(mode) && is_submodule_ignored(concatpath, options))
                return;

        /* This may look odd, but it is a preparation for
         * feeding "there are unchanged files which should
         * not produce diffs, but when you are doing copy
         * detection you would need them, so here they are"
         * entries to the diff-core.  They will be prefixed
         * with something like '=' or '*' (I haven't decided
         * which but should not make any difference).
         * Feeding the same new and old to diff_change()
         * also has the same effect.
         * Before the final output happens, they are pruned after
         * merged into rename/copy pairs as appropriate.
         */
        if (DIFF_OPT_TST(options, REVERSE_DIFF))
                addremove = (addremove == '+' ? '-' :
                             addremove == '-' ? '+' : addremove);

        if (options->prefix &&
            strncmp(concatpath, options->prefix, options->prefix_length))
                return;

        one = alloc_filespec(concatpath);
        two = alloc_filespec(concatpath);

        if (addremove != '+')
                fill_filespec(one, sha1, sha1_valid, mode);
        if (addremove != '-') {
                fill_filespec(two, sha1, sha1_valid, mode);
                two->dirty_submodule = dirty_submodule;
        }

        diff_queue(&diff_queued_diff, one, two);
        if (!DIFF_OPT_TST(options, DIFF_FROM_CONTENTS))
                DIFF_OPT_SET(options, HAS_CHANGES);
}

void diff_change(struct diff_options *options,
                 unsigned old_mode, unsigned new_mode,
                 const unsigned char *old_sha1,
                 const unsigned char *new_sha1,
                 int old_sha1_valid, int new_sha1_valid,
                 const char *concatpath,
                 unsigned old_dirty_submodule, unsigned new_dirty_submodule)
{
        struct diff_filespec *one, *two;
        struct diff_filepair *p;

        if (S_ISGITLINK(old_mode) && S_ISGITLINK(new_mode) &&
            is_submodule_ignored(concatpath, options))
                return;

        if (DIFF_OPT_TST(options, REVERSE_DIFF)) {
                unsigned tmp;
                const unsigned char *tmp_c;
                tmp = old_mode; old_mode = new_mode; new_mode = tmp;
                tmp_c = old_sha1; old_sha1 = new_sha1; new_sha1 = tmp_c;
                tmp = old_sha1_valid; old_sha1_valid = new_sha1_valid;
                        new_sha1_valid = tmp;
                tmp = old_dirty_submodule; old_dirty_submodule = new_dirty_submodule;
                        new_dirty_submodule = tmp;
        }

        if (options->prefix &&
            strncmp(concatpath, options->prefix, options->prefix_length))
                return;

        one = alloc_filespec(concatpath);
        two = alloc_filespec(concatpath);
        fill_filespec(one, old_sha1, old_sha1_valid, old_mode);
        fill_filespec(two, new_sha1, new_sha1_valid, new_mode);
        one->dirty_submodule = old_dirty_submodule;
        two->dirty_submodule = new_dirty_submodule;
        p = diff_queue(&diff_queued_diff, one, two);

        if (DIFF_OPT_TST(options, DIFF_FROM_CONTENTS))
                return;

        if (DIFF_OPT_TST(options, QUICK) && options->skip_stat_unmatch &&
            !diff_filespec_check_stat_unmatch(p))
                return;

        DIFF_OPT_SET(options, HAS_CHANGES);
}

struct diff_filepair *diff_unmerge(struct diff_options *options, const char *path)
{
        struct diff_filepair *pair;
        struct diff_filespec *one, *two;

        if (options->prefix &&
            strncmp(path, options->prefix, options->prefix_length))
                return NULL;

        one = alloc_filespec(path);
        two = alloc_filespec(path);
        pair = diff_queue(&diff_queued_diff, one, two);
        pair->is_unmerged = 1;
        return pair;
}

static char *run_textconv(const char *pgm, struct diff_filespec *spec,
                size_t *outsize)
{
        struct diff_tempfile *temp;
        const char *argv[3];
        const char **arg = argv;
        struct child_process child = CHILD_PROCESS_INIT;
        struct strbuf buf = STRBUF_INIT;
        int err = 0;

        temp = prepare_temp_file(spec->path, spec);
        *arg++ = pgm;
        *arg++ = temp->name;
        *arg = NULL;

        child.use_shell = 1;
        child.argv = argv;
        child.out = -1;
        if (start_command(&child)) {
                remove_tempfile();
                return NULL;
        }

        if (strbuf_read(&buf, child.out, 0) < 0)
                err = error("error reading from textconv command '%s'", pgm);
        close(child.out);

        if (finish_command(&child) || err) {
                strbuf_release(&buf);
                remove_tempfile();
                return NULL;
        }
        remove_tempfile();

        return strbuf_detach(&buf, outsize);
}

size_t fill_textconv(struct userdiff_driver *driver,
                     struct diff_filespec *df,
                     char **outbuf)
{
        size_t size;

        if (!driver) {
                if (!DIFF_FILE_VALID(df)) {
                        *outbuf = "";
                        return 0;
                }
                if (diff_populate_filespec(df, 0))
                        die("unable to read files to diff");
                *outbuf = df->data;
                return df->size;
        }

        if (!driver->textconv)
                die("BUG: fill_textconv called with non-textconv driver");

        if (driver->textconv_cache && df->oid_valid) {
                *outbuf = notes_cache_get(driver->textconv_cache,
                                          df->oid.hash,
                                          &size);
                if (*outbuf)
                        return size;
        }

        *outbuf = run_textconv(driver->textconv, df, &size);
        if (!*outbuf)
                die("unable to read files to diff");

        if (driver->textconv_cache && df->oid_valid) {
                /* ignore errors, as we might be in a readonly repository */
                notes_cache_put(driver->textconv_cache, df->oid.hash, *outbuf,
                                size);
                /*
                 * we could save up changes and flush them all at the end,
                 * but we would need an extra call after all diffing is done.
                 * Since generating a cache entry is the slow path anyway,
                 * this extra overhead probably isn't a big deal.
                 */
                notes_cache_write(driver->textconv_cache);
        }

        return size;
}

void setup_diff_pager(struct diff_options *opt)
{
        /*
         * If the user asked for our exit code, then either they want --quiet
         * or --exit-code. We should definitely not bother with a pager in the
         * former case, as we will generate no output. Since we still properly
         * report our exit code even when a pager is run, we _could_ run a
         * pager with --exit-code. But since we have not done so historically,
         * and because it is easy to find people oneline advising "git diff
         * --exit-code" in hooks and other scripts, we do not do so.
         */
        if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
            check_pager_config("diff") != 0)
                setup_pager();
}