compat/mingw: support MSys2-based MinGW build

[git/debian.git] / builtin / log.c

/*
 * Builtin "git log" and related commands (show, whatchanged)
 *
 * (C) Copyright 2006 Linus Torvalds
 *               2006 Junio Hamano
 */
#include "cache.h"
#include "refs.h"
#include "color.h"
#include "commit.h"
#include "diff.h"
#include "revision.h"
#include "log-tree.h"
#include "builtin.h"
#include "tag.h"
#include "reflog-walk.h"
#include "patch-ids.h"
#include "run-command.h"
#include "shortlog.h"
#include "remote.h"
#include "string-list.h"
#include "parse-options.h"
#include "line-log.h"
#include "branch.h"
#include "streaming.h"
#include "version.h"
#include "mailmap.h"
#include "gpg-interface.h"

/* Set a default date-time format for git log ("log.date" config variable) */
static const char *default_date_mode = NULL;

static int default_abbrev_commit;
static int default_show_root = 1;
static int default_follow;
static int decoration_style;
static int decoration_given;
static int use_mailmap_config;
static const char *fmt_patch_subject_prefix = "PATCH";
static const char *fmt_pretty;

static const char * const builtin_log_usage[] = {
        N_("git log [<options>] [<revision-range>] [[--] <path>...]"),
        N_("git show [<options>] <object>..."),
        NULL
};

struct line_opt_callback_data {
        struct rev_info *rev;
        const char *prefix;
        struct string_list args;
};

static int parse_decoration_style(const char *var, const char *value)
{
        switch (git_config_maybe_bool(var, value)) {
        case 1:
                return DECORATE_SHORT_REFS;
        case 0:
                return 0;
        default:
                break;
        }
        if (!strcmp(value, "full"))
                return DECORATE_FULL_REFS;
        else if (!strcmp(value, "short"))
                return DECORATE_SHORT_REFS;
        else if (!strcmp(value, "auto"))
                return (isatty(1) || pager_in_use()) ? DECORATE_SHORT_REFS : 0;
        return -1;
}

static int decorate_callback(const struct option *opt, const char *arg, int unset)
{
        if (unset)
                decoration_style = 0;
        else if (arg)
                decoration_style = parse_decoration_style("command line", arg);
        else
                decoration_style = DECORATE_SHORT_REFS;

        if (decoration_style < 0)
                die(_("invalid --decorate option: %s"), arg);

        decoration_given = 1;

        return 0;
}

static int log_line_range_callback(const struct option *option, const char *arg, int unset)
{
        struct line_opt_callback_data *data = option->value;

        if (!arg)
                return -1;

        data->rev->line_level_traverse = 1;
        string_list_append(&data->args, arg);

        return 0;
}

static void cmd_log_init_defaults(struct rev_info *rev)
{
        if (fmt_pretty)
                get_commit_format(fmt_pretty, rev);
        if (default_follow)
                DIFF_OPT_SET(&rev->diffopt, DEFAULT_FOLLOW_RENAMES);
        rev->verbose_header = 1;
        DIFF_OPT_SET(&rev->diffopt, RECURSIVE);
        rev->diffopt.stat_width = -1; /* use full terminal width */
        rev->diffopt.stat_graph_width = -1; /* respect statGraphWidth config */
        rev->abbrev_commit = default_abbrev_commit;
        rev->show_root_diff = default_show_root;
        rev->subject_prefix = fmt_patch_subject_prefix;
        DIFF_OPT_SET(&rev->diffopt, ALLOW_TEXTCONV);

        if (default_date_mode)
                parse_date_format(default_date_mode, &rev->date_mode);
        rev->diffopt.touched_flags = 0;
}

static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
                         struct rev_info *rev, struct setup_revision_opt *opt)
{
        struct userformat_want w;
        int quiet = 0, source = 0, mailmap = 0;
        static struct line_opt_callback_data line_cb = {NULL, NULL, STRING_LIST_INIT_DUP};

        const struct option builtin_log_options[] = {
                OPT__QUIET(&quiet, N_("suppress diff output")),
                OPT_BOOL(0, "source", &source, N_("show source")),
                OPT_BOOL(0, "use-mailmap", &mailmap, N_("Use mail map file")),
                { OPTION_CALLBACK, 0, "decorate", NULL, NULL, N_("decorate options"),
                  PARSE_OPT_OPTARG, decorate_callback},
                OPT_CALLBACK('L', NULL, &line_cb, "n,m:file",
                             N_("Process line range n,m in file, counting from 1"),
                             log_line_range_callback),
                OPT_END()
        };

        line_cb.rev = rev;
        line_cb.prefix = prefix;

        mailmap = use_mailmap_config;
        argc = parse_options(argc, argv, prefix,
                             builtin_log_options, builtin_log_usage,
                             PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN |
                             PARSE_OPT_KEEP_DASHDASH);

        if (quiet)
                rev->diffopt.output_format |= DIFF_FORMAT_NO_OUTPUT;
        argc = setup_revisions(argc, argv, rev, opt);

        /* Any arguments at this point are not recognized */
        if (argc > 1)
                die(_("unrecognized argument: %s"), argv[1]);

        memset(&w, 0, sizeof(w));
        userformat_find_requirements(NULL, &w);

        if (!rev->show_notes_given && (!rev->pretty_given || w.notes))
                rev->show_notes = 1;
        if (rev->show_notes)
                init_display_notes(&rev->notes_opt);

        if (rev->diffopt.pickaxe || rev->diffopt.filter ||
            DIFF_OPT_TST(&rev->diffopt, FOLLOW_RENAMES))
                rev->always_show_header = 0;

        if (source)
                rev->show_source = 1;

        if (mailmap) {
                rev->mailmap = xcalloc(1, sizeof(struct string_list));
                read_mailmap(rev->mailmap, NULL);
        }

        if (rev->pretty_given && rev->commit_format == CMIT_FMT_RAW) {
                /*
                 * "log --pretty=raw" is special; ignore UI oriented
                 * configuration variables such as decoration.
                 */
                if (!decoration_given)
                        decoration_style = 0;
                if (!rev->abbrev_commit_given)
                        rev->abbrev_commit = 0;
        }

        if (decoration_style) {
                rev->show_decorations = 1;
                load_ref_decorations(decoration_style);
        }

        if (rev->line_level_traverse)
                line_log_init(rev, line_cb.prefix, &line_cb.args);

        setup_pager();
}

static void cmd_log_init(int argc, const char **argv, const char *prefix,
                         struct rev_info *rev, struct setup_revision_opt *opt)
{
        cmd_log_init_defaults(rev);
        cmd_log_init_finish(argc, argv, prefix, rev, opt);
}

/*
 * This gives a rough estimate for how many commits we
 * will print out in the list.
 */
static int estimate_commit_count(struct rev_info *rev, struct commit_list *list)
{
        int n = 0;

        while (list) {
                struct commit *commit = list->item;
                unsigned int flags = commit->object.flags;
                list = list->next;
                if (!(flags & (TREESAME | UNINTERESTING)))
                        n++;
        }
        return n;
}

static void show_early_header(struct rev_info *rev, const char *stage, int nr)
{
        if (rev->shown_one) {
                rev->shown_one = 0;
                if (rev->commit_format != CMIT_FMT_ONELINE)
                        putchar(rev->diffopt.line_termination);
        }
        printf(_("Final output: %d %s\n"), nr, stage);
}

static struct itimerval early_output_timer;

static void log_show_early(struct rev_info *revs, struct commit_list *list)
{
        int i = revs->early_output;
        int show_header = 1;

        sort_in_topological_order(&list, revs->sort_order);
        while (list && i) {
                struct commit *commit = list->item;
                switch (simplify_commit(revs, commit)) {
                case commit_show:
                        if (show_header) {
                                int n = estimate_commit_count(revs, list);
                                show_early_header(revs, "incomplete", n);
                                show_header = 0;
                        }
                        log_tree_commit(revs, commit);
                        i--;
                        break;
                case commit_ignore:
                        break;
                case commit_error:
                        return;
                }
                list = list->next;
        }

        /* Did we already get enough commits for the early output? */
        if (!i)
                return;

        /*
         * ..if no, then repeat it twice a second until we
         * do.
         *
         * NOTE! We don't use "it_interval", because if the
         * reader isn't listening, we want our output to be
         * throttled by the writing, and not have the timer
         * trigger every second even if we're blocked on a
         * reader!
         */
        early_output_timer.it_value.tv_sec = 0;
        early_output_timer.it_value.tv_usec = 500000;
        setitimer(ITIMER_REAL, &early_output_timer, NULL);
}

static void early_output(int signal)
{
        show_early_output = log_show_early;
}

static void setup_early_output(struct rev_info *rev)
{
        struct sigaction sa;

        /*
         * Set up the signal handler, minimally intrusively:
         * we only set a single volatile integer word (not
         * using sigatomic_t - trying to avoid unnecessary
         * system dependencies and headers), and using
         * SA_RESTART.
         */
        memset(&sa, 0, sizeof(sa));
        sa.sa_handler = early_output;
        sigemptyset(&sa.sa_mask);
        sa.sa_flags = SA_RESTART;
        sigaction(SIGALRM, &sa, NULL);

        /*
         * If we can get the whole output in less than a
         * tenth of a second, don't even bother doing the
         * early-output thing..
         *
         * This is a one-time-only trigger.
         */
        early_output_timer.it_value.tv_sec = 0;
        early_output_timer.it_value.tv_usec = 100000;
        setitimer(ITIMER_REAL, &early_output_timer, NULL);
}

static void finish_early_output(struct rev_info *rev)
{
        int n = estimate_commit_count(rev, rev->commits);
        signal(SIGALRM, SIG_IGN);
        show_early_header(rev, "done", n);
}

static int cmd_log_walk(struct rev_info *rev)
{
        struct commit *commit;
        int saved_nrl = 0;
        int saved_dcctc = 0;

        if (rev->early_output)
                setup_early_output(rev);

        if (prepare_revision_walk(rev))
                die(_("revision walk setup failed"));

        if (rev->early_output)
                finish_early_output(rev);

        /*
         * For --check and --exit-code, the exit code is based on CHECK_FAILED
         * and HAS_CHANGES being accumulated in rev->diffopt, so be careful to
         * retain that state information if replacing rev->diffopt in this loop
         */
        while ((commit = get_revision(rev)) != NULL) {
                if (!log_tree_commit(rev, commit) && rev->max_count >= 0)
                        /*
                         * We decremented max_count in get_revision,
                         * but we didn't actually show the commit.
                         */
                        rev->max_count++;
                if (!rev->reflog_info) {
                        /* we allow cycles in reflog ancestry */
                        free_commit_buffer(commit);
                }
                free_commit_list(commit->parents);
                commit->parents = NULL;
                if (saved_nrl < rev->diffopt.needed_rename_limit)
                        saved_nrl = rev->diffopt.needed_rename_limit;
                if (rev->diffopt.degraded_cc_to_c)
                        saved_dcctc = 1;
        }
        rev->diffopt.degraded_cc_to_c = saved_dcctc;
        rev->diffopt.needed_rename_limit = saved_nrl;

        if (rev->diffopt.output_format & DIFF_FORMAT_CHECKDIFF &&
            DIFF_OPT_TST(&rev->diffopt, CHECK_FAILED)) {
                return 02;
        }
        return diff_result_code(&rev->diffopt, 0);
}

static int git_log_config(const char *var, const char *value, void *cb)
{
        const char *slot_name;

        if (!strcmp(var, "format.pretty"))
                return git_config_string(&fmt_pretty, var, value);
        if (!strcmp(var, "format.subjectprefix"))
                return git_config_string(&fmt_patch_subject_prefix, var, value);
        if (!strcmp(var, "log.abbrevcommit")) {
                default_abbrev_commit = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "log.date"))
                return git_config_string(&default_date_mode, var, value);
        if (!strcmp(var, "log.decorate")) {
                decoration_style = parse_decoration_style(var, value);
                if (decoration_style < 0)
                        decoration_style = 0; /* maybe warn? */
                return 0;
        }
        if (!strcmp(var, "log.showroot")) {
                default_show_root = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "log.follow")) {
                default_follow = git_config_bool(var, value);
                return 0;
        }
        if (skip_prefix(var, "color.decorate.", &slot_name))
                return parse_decorate_color_config(var, slot_name, value);
        if (!strcmp(var, "log.mailmap")) {
                use_mailmap_config = git_config_bool(var, value);
                return 0;
        }

        if (grep_config(var, value, cb) < 0)
                return -1;
        if (git_gpg_config(var, value, cb) < 0)
                return -1;
        return git_diff_ui_config(var, value, cb);
}

int cmd_whatchanged(int argc, const char **argv, const char *prefix)
{
        struct rev_info rev;
        struct setup_revision_opt opt;

        init_grep_defaults();
        git_config(git_log_config, NULL);

        init_revisions(&rev, prefix);
        rev.diff = 1;
        rev.simplify_history = 0;
        memset(&opt, 0, sizeof(opt));
        opt.def = "HEAD";
        opt.revarg_opt = REVARG_COMMITTISH;
        cmd_log_init(argc, argv, prefix, &rev, &opt);
        if (!rev.diffopt.output_format)
                rev.diffopt.output_format = DIFF_FORMAT_RAW;
        return cmd_log_walk(&rev);
}

static void show_tagger(char *buf, int len, struct rev_info *rev)
{
        struct strbuf out = STRBUF_INIT;
        struct pretty_print_context pp = {0};

        pp.fmt = rev->commit_format;
        pp.date_mode = rev->date_mode;
        pp_user_info(&pp, "Tagger", &out, buf, get_log_output_encoding());
        printf("%s", out.buf);
        strbuf_release(&out);
}

static int show_blob_object(const unsigned char *sha1, struct rev_info *rev, const char *obj_name)
{
        unsigned char sha1c[20];
        struct object_context obj_context;
        char *buf;
        unsigned long size;

        fflush(stdout);
        if (!DIFF_OPT_TOUCHED(&rev->diffopt, ALLOW_TEXTCONV) ||
            !DIFF_OPT_TST(&rev->diffopt, ALLOW_TEXTCONV))
                return stream_blob_to_fd(1, sha1, NULL, 0);

        if (get_sha1_with_context(obj_name, 0, sha1c, &obj_context))
                die(_("Not a valid object name %s"), obj_name);
        if (!obj_context.path[0] ||
            !textconv_object(obj_context.path, obj_context.mode, sha1c, 1, &buf, &size))
                return stream_blob_to_fd(1, sha1, NULL, 0);

        if (!buf)
                die(_("git show %s: bad file"), obj_name);

        write_or_die(1, buf, size);
        return 0;
}

static int show_tag_object(const unsigned char *sha1, struct rev_info *rev)
{
        unsigned long size;
        enum object_type type;
        char *buf = read_sha1_file(sha1, &type, &size);
        int offset = 0;

        if (!buf)
                return error(_("Could not read object %s"), sha1_to_hex(sha1));

        assert(type == OBJ_TAG);
        while (offset < size && buf[offset] != '\n') {
                int new_offset = offset + 1;
                while (new_offset < size && buf[new_offset++] != '\n')
                        ; /* do nothing */
                if (starts_with(buf + offset, "tagger "))
                        show_tagger(buf + offset + 7,
                                    new_offset - offset - 7, rev);
                offset = new_offset;
        }

        if (offset < size)
                fwrite(buf + offset, size - offset, 1, stdout);
        free(buf);
        return 0;
}

static int show_tree_object(const unsigned char *sha1,
                struct strbuf *base,
                const char *pathname, unsigned mode, int stage, void *context)
{
        printf("%s%s\n", pathname, S_ISDIR(mode) ? "/" : "");
        return 0;
}

static void show_setup_revisions_tweak(struct rev_info *rev,
                                       struct setup_revision_opt *opt)
{
        if (rev->ignore_merges) {
                /* There was no "-m" on the command line */
                rev->ignore_merges = 0;
                if (!rev->first_parent_only && !rev->combine_merges) {
                        /* No "--first-parent", "-c", or "--cc" */
                        rev->combine_merges = 1;
                        rev->dense_combined_merges = 1;
                }
        }
        if (!rev->diffopt.output_format)
                rev->diffopt.output_format = DIFF_FORMAT_PATCH;
}

int cmd_show(int argc, const char **argv, const char *prefix)
{
        struct rev_info rev;
        struct object_array_entry *objects;
        struct setup_revision_opt opt;
        struct pathspec match_all;
        int i, count, ret = 0;

        init_grep_defaults();
        git_config(git_log_config, NULL);

        memset(&match_all, 0, sizeof(match_all));
        init_revisions(&rev, prefix);
        rev.diff = 1;
        rev.always_show_header = 1;
        rev.no_walk = REVISION_WALK_NO_WALK_SORTED;
        rev.diffopt.stat_width = -1;    /* Scale to real terminal size */

        memset(&opt, 0, sizeof(opt));
        opt.def = "HEAD";
        opt.tweak = show_setup_revisions_tweak;
        cmd_log_init(argc, argv, prefix, &rev, &opt);

        if (!rev.no_walk)
                return cmd_log_walk(&rev);

        count = rev.pending.nr;
        objects = rev.pending.objects;
        for (i = 0; i < count && !ret; i++) {
                struct object *o = objects[i].item;
                const char *name = objects[i].name;
                switch (o->type) {
                case OBJ_BLOB:
                        ret = show_blob_object(o->oid.hash, &rev, name);
                        break;
                case OBJ_TAG: {
                        struct tag *t = (struct tag *)o;

                        if (rev.shown_one)
                                putchar('\n');
                        printf("%stag %s%s\n",
                                        diff_get_color_opt(&rev.diffopt, DIFF_COMMIT),
                                        t->tag,
                                        diff_get_color_opt(&rev.diffopt, DIFF_RESET));
                        ret = show_tag_object(o->oid.hash, &rev);
                        rev.shown_one = 1;
                        if (ret)
                                break;
                        o = parse_object(t->tagged->oid.hash);
                        if (!o)
                                ret = error(_("Could not read object %s"),
                                            oid_to_hex(&t->tagged->oid));
                        objects[i].item = o;
                        i--;
                        break;
                }
                case OBJ_TREE:
                        if (rev.shown_one)
                                putchar('\n');
                        printf("%stree %s%s\n\n",
                                        diff_get_color_opt(&rev.diffopt, DIFF_COMMIT),
                                        name,
                                        diff_get_color_opt(&rev.diffopt, DIFF_RESET));
                        read_tree_recursive((struct tree *)o, "", 0, 0, &match_all,
                                        show_tree_object, NULL);
                        rev.shown_one = 1;
                        break;
                case OBJ_COMMIT:
                        rev.pending.nr = rev.pending.alloc = 0;
                        rev.pending.objects = NULL;
                        add_object_array(o, name, &rev.pending);
                        ret = cmd_log_walk(&rev);
                        break;
                default:
                        ret = error(_("Unknown type: %d"), o->type);
                }
        }
        free(objects);
        return ret;
}

/*
 * This is equivalent to "git log -g --abbrev-commit --pretty=oneline"
 */
int cmd_log_reflog(int argc, const char **argv, const char *prefix)
{
        struct rev_info rev;
        struct setup_revision_opt opt;

        init_grep_defaults();
        git_config(git_log_config, NULL);

        init_revisions(&rev, prefix);
        init_reflog_walk(&rev.reflog_info);
        rev.verbose_header = 1;
        memset(&opt, 0, sizeof(opt));
        opt.def = "HEAD";
        cmd_log_init_defaults(&rev);
        rev.abbrev_commit = 1;
        rev.commit_format = CMIT_FMT_ONELINE;
        rev.use_terminator = 1;
        rev.always_show_header = 1;
        cmd_log_init_finish(argc, argv, prefix, &rev, &opt);

        return cmd_log_walk(&rev);
}

static void log_setup_revisions_tweak(struct rev_info *rev,
                                      struct setup_revision_opt *opt)
{
        if (DIFF_OPT_TST(&rev->diffopt, DEFAULT_FOLLOW_RENAMES) &&
            rev->prune_data.nr == 1)
                DIFF_OPT_SET(&rev->diffopt, FOLLOW_RENAMES);

        /* Turn --cc/-c into -p --cc/-c when -p was not given */
        if (!rev->diffopt.output_format && rev->combine_merges)
                rev->diffopt.output_format = DIFF_FORMAT_PATCH;

        /* Turn -m on when --cc/-c was given */
        if (rev->combine_merges)
                rev->ignore_merges = 0;
}

int cmd_log(int argc, const char **argv, const char *prefix)
{
        struct rev_info rev;
        struct setup_revision_opt opt;

        init_grep_defaults();
        git_config(git_log_config, NULL);

        init_revisions(&rev, prefix);
        rev.always_show_header = 1;
        memset(&opt, 0, sizeof(opt));
        opt.def = "HEAD";
        opt.revarg_opt = REVARG_COMMITTISH;
        opt.tweak = log_setup_revisions_tweak;
        cmd_log_init(argc, argv, prefix, &rev, &opt);
        return cmd_log_walk(&rev);
}

/* format-patch */

static const char *fmt_patch_suffix = ".patch";
static int numbered = 0;
static int auto_number = 1;

static char *default_attach = NULL;

static struct string_list extra_hdr;
static struct string_list extra_to;
static struct string_list extra_cc;

static void add_header(const char *value)
{
        struct string_list_item *item;
        int len = strlen(value);
        while (len && value[len - 1] == '\n')
                len--;

        if (!strncasecmp(value, "to: ", 4)) {
                item = string_list_append(&extra_to, value + 4);
                len -= 4;
        } else if (!strncasecmp(value, "cc: ", 4)) {
                item = string_list_append(&extra_cc, value + 4);
                len -= 4;
        } else {
                item = string_list_append(&extra_hdr, value);
        }

        item->string[len] = '\0';
}

#define THREAD_SHALLOW 1
#define THREAD_DEEP 2
static int thread;
static int do_signoff;
static const char *signature = git_version_string;
static const char *signature_file;
static int config_cover_letter;

enum {
        COVER_UNSET,
        COVER_OFF,
        COVER_ON,
        COVER_AUTO
};

static int git_format_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "format.headers")) {
                if (!value)
                        die(_("format.headers without value"));
                add_header(value);
                return 0;
        }
        if (!strcmp(var, "format.suffix"))
                return git_config_string(&fmt_patch_suffix, var, value);
        if (!strcmp(var, "format.to")) {
                if (!value)
                        return config_error_nonbool(var);
                string_list_append(&extra_to, value);
                return 0;
        }
        if (!strcmp(var, "format.cc")) {
                if (!value)
                        return config_error_nonbool(var);
                string_list_append(&extra_cc, value);
                return 0;
        }
        if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff") ||
            !strcmp(var, "color.ui") || !strcmp(var, "diff.submodule")) {
                return 0;
        }
        if (!strcmp(var, "format.numbered")) {
                if (value && !strcasecmp(value, "auto")) {
                        auto_number = 1;
                        return 0;
                }
                numbered = git_config_bool(var, value);
                auto_number = auto_number && numbered;
                return 0;
        }
        if (!strcmp(var, "format.attach")) {
                if (value && *value)
                        default_attach = xstrdup(value);
                else
                        default_attach = xstrdup(git_version_string);
                return 0;
        }
        if (!strcmp(var, "format.thread")) {
                if (value && !strcasecmp(value, "deep")) {
                        thread = THREAD_DEEP;
                        return 0;
                }
                if (value && !strcasecmp(value, "shallow")) {
                        thread = THREAD_SHALLOW;
                        return 0;
                }
                thread = git_config_bool(var, value) && THREAD_SHALLOW;
                return 0;
        }
        if (!strcmp(var, "format.signoff")) {
                do_signoff = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "format.signature"))
                return git_config_string(&signature, var, value);
        if (!strcmp(var, "format.signaturefile"))
                return git_config_pathname(&signature_file, var, value);
        if (!strcmp(var, "format.coverletter")) {
                if (value && !strcasecmp(value, "auto")) {
                        config_cover_letter = COVER_AUTO;
                        return 0;
                }
                config_cover_letter = git_config_bool(var, value) ? COVER_ON : COVER_OFF;
                return 0;
        }

        return git_log_config(var, value, cb);
}

static FILE *realstdout = NULL;
static const char *output_directory = NULL;
static int outdir_offset;

static int reopen_stdout(struct commit *commit, const char *subject,
                         struct rev_info *rev, int quiet)
{
        struct strbuf filename = STRBUF_INIT;
        int suffix_len = strlen(rev->patch_suffix) + 1;

        if (output_directory) {
                strbuf_addstr(&filename, output_directory);
                if (filename.len >=
                    PATH_MAX - FORMAT_PATCH_NAME_MAX - suffix_len)
                        return error(_("name of output directory is too long"));
                strbuf_complete(&filename, '/');
        }

        if (rev->numbered_files)
                strbuf_addf(&filename, "%d", rev->nr);
        else if (commit)
                fmt_output_commit(&filename, commit, rev);
        else
                fmt_output_subject(&filename, subject, rev);

        if (!quiet)
                fprintf(realstdout, "%s\n", filename.buf + outdir_offset);

        if (freopen(filename.buf, "w", stdout) == NULL)
                return error(_("Cannot open patch file %s"), filename.buf);

        strbuf_release(&filename);
        return 0;
}

static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids)
{
        struct rev_info check_rev;
        struct commit *commit, *c1, *c2;
        struct object *o1, *o2;
        unsigned flags1, flags2;

        if (rev->pending.nr != 2)
                die(_("Need exactly one range."));

        o1 = rev->pending.objects[0].item;
        o2 = rev->pending.objects[1].item;
        flags1 = o1->flags;
        flags2 = o2->flags;
        c1 = lookup_commit_reference(o1->oid.hash);
        c2 = lookup_commit_reference(o2->oid.hash);

        if ((flags1 & UNINTERESTING) == (flags2 & UNINTERESTING))
                die(_("Not a range."));

        init_patch_ids(ids);

        /* given a range a..b get all patch ids for b..a */
        init_revisions(&check_rev, rev->prefix);
        check_rev.max_parents = 1;
        o1->flags ^= UNINTERESTING;
        o2->flags ^= UNINTERESTING;
        add_pending_object(&check_rev, o1, "o1");
        add_pending_object(&check_rev, o2, "o2");
        if (prepare_revision_walk(&check_rev))
                die(_("revision walk setup failed"));

        while ((commit = get_revision(&check_rev)) != NULL) {
                add_commit_patch_id(commit, ids);
        }

        /* reset for next revision walk */
        clear_commit_marks(c1, SEEN | UNINTERESTING | SHOWN | ADDED);
        clear_commit_marks(c2, SEEN | UNINTERESTING | SHOWN | ADDED);
        o1->flags = flags1;
        o2->flags = flags2;
}

static void gen_message_id(struct rev_info *info, char *base)
{
        struct strbuf buf = STRBUF_INIT;
        strbuf_addf(&buf, "%s.%lu.git.%s", base,
                    (unsigned long) time(NULL),
                    git_committer_info(IDENT_NO_NAME|IDENT_NO_DATE|IDENT_STRICT));
        info->message_id = strbuf_detach(&buf, NULL);
}

static void print_signature(void)
{
        if (!signature || !*signature)
                return;

        printf("-- \n%s", signature);
        if (signature[strlen(signature)-1] != '\n')
                putchar('\n');
        putchar('\n');
}

static void add_branch_description(struct strbuf *buf, const char *branch_name)
{
        struct strbuf desc = STRBUF_INIT;
        if (!branch_name || !*branch_name)
                return;
        read_branch_desc(&desc, branch_name);
        if (desc.len) {
                strbuf_addch(buf, '\n');
                strbuf_addbuf(buf, &desc);
                strbuf_addch(buf, '\n');
        }
        strbuf_release(&desc);
}

static char *find_branch_name(struct rev_info *rev)
{
        int i, positive = -1;
        struct object_id branch_oid;
        const struct object_id *tip_oid;
        const char *ref, *v;
        char *full_ref, *branch = NULL;

        for (i = 0; i < rev->cmdline.nr; i++) {
                if (rev->cmdline.rev[i].flags & UNINTERESTING)
                        continue;
                if (positive < 0)
                        positive = i;
                else
                        return NULL;
        }
        if (positive < 0)
                return NULL;
        ref = rev->cmdline.rev[positive].name;
        tip_oid = &rev->cmdline.rev[positive].item->oid;
        if (dwim_ref(ref, strlen(ref), branch_oid.hash, &full_ref) &&
            skip_prefix(full_ref, "refs/heads/", &v) &&
            !oidcmp(tip_oid, &branch_oid))
                branch = xstrdup(v);
        free(full_ref);
        return branch;
}

static void make_cover_letter(struct rev_info *rev, int use_stdout,
                              struct commit *origin,
                              int nr, struct commit **list,
                              const char *branch_name,
                              int quiet)
{
        const char *committer;
        const char *body = "*** SUBJECT HERE ***\n\n*** BLURB HERE ***\n";
        const char *msg;
        struct shortlog log;
        struct strbuf sb = STRBUF_INIT;
        int i;
        const char *encoding = "UTF-8";
        struct diff_options opts;
        int need_8bit_cte = 0;
        struct pretty_print_context pp = {0};
        struct commit *head = list[0];

        if (rev->commit_format != CMIT_FMT_EMAIL)
                die(_("Cover letter needs email format"));

        committer = git_committer_info(0);

        if (!use_stdout &&
            reopen_stdout(NULL, rev->numbered_files ? NULL : "cover-letter", rev, quiet))
                return;

        log_write_email_headers(rev, head, &pp.subject, &pp.after_subject,
                                &need_8bit_cte);

        for (i = 0; !need_8bit_cte && i < nr; i++) {
                const char *buf = get_commit_buffer(list[i], NULL);
                if (has_non_ascii(buf))
                        need_8bit_cte = 1;
                unuse_commit_buffer(list[i], buf);
        }

        if (!branch_name)
                branch_name = find_branch_name(rev);

        msg = body;
        pp.fmt = CMIT_FMT_EMAIL;
        pp.date_mode.type = DATE_RFC2822;
        pp_user_info(&pp, NULL, &sb, committer, encoding);
        pp_title_line(&pp, &msg, &sb, encoding, need_8bit_cte);
        pp_remainder(&pp, &msg, &sb, 0);
        add_branch_description(&sb, branch_name);
        printf("%s\n", sb.buf);

        strbuf_release(&sb);

        shortlog_init(&log);
        log.wrap_lines = 1;
        log.wrap = 72;
        log.in1 = 2;
        log.in2 = 4;
        for (i = 0; i < nr; i++)
                shortlog_add_commit(&log, list[i]);

        shortlog_output(&log);

        /*
         * We can only do diffstat with a unique reference point
         */
        if (!origin)
                return;

        memcpy(&opts, &rev->diffopt, sizeof(opts));
        opts.output_format = DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;

        diff_setup_done(&opts);

        diff_tree_sha1(origin->tree->object.oid.hash,
                       head->tree->object.oid.hash,
                       "", &opts);
        diffcore_std(&opts);
        diff_flush(&opts);

        printf("\n");
        print_signature();
}

static const char *clean_message_id(const char *msg_id)
{
        char ch;
        const char *a, *z, *m;

        m = msg_id;
        while ((ch = *m) && (isspace(ch) || (ch == '<')))
                m++;
        a = m;
        z = NULL;
        while ((ch = *m)) {
                if (!isspace(ch) && (ch != '>'))
                        z = m;
                m++;
        }
        if (!z)
                die(_("insane in-reply-to: %s"), msg_id);
        if (++z == m)
                return a;
        return xmemdupz(a, z - a);
}

static const char *set_outdir(const char *prefix, const char *output_directory)
{
        if (output_directory && is_absolute_path(output_directory))
                return output_directory;

        if (!prefix || !*prefix) {
                if (output_directory)
                        return output_directory;
                /* The user did not explicitly ask for "./" */
                outdir_offset = 2;
                return "./";
        }

        outdir_offset = strlen(prefix);
        if (!output_directory)
                return prefix;

        return xstrdup(prefix_filename(prefix, outdir_offset,
                                       output_directory));
}

static const char * const builtin_format_patch_usage[] = {
        N_("git format-patch [<options>] [<since> | <revision-range>]"),
        NULL
};

static int keep_subject = 0;

static int keep_callback(const struct option *opt, const char *arg, int unset)
{
        ((struct rev_info *)opt->value)->total = -1;
        keep_subject = 1;
        return 0;
}

static int subject_prefix = 0;

static int subject_prefix_callback(const struct option *opt, const char *arg,
                            int unset)
{
        subject_prefix = 1;
        ((struct rev_info *)opt->value)->subject_prefix = arg;
        return 0;
}

static int numbered_cmdline_opt = 0;

static int numbered_callback(const struct option *opt, const char *arg,
                             int unset)
{
        *(int *)opt->value = numbered_cmdline_opt = unset ? 0 : 1;
        if (unset)
                auto_number =  0;
        return 0;
}

static int no_numbered_callback(const struct option *opt, const char *arg,
                                int unset)
{
        return numbered_callback(opt, arg, 1);
}

static int output_directory_callback(const struct option *opt, const char *arg,
                              int unset)
{
        const char **dir = (const char **)opt->value;
        if (*dir)
                die(_("Two output directories?"));
        *dir = arg;
        return 0;
}

static int thread_callback(const struct option *opt, const char *arg, int unset)
{
        int *thread = (int *)opt->value;
        if (unset)
                *thread = 0;
        else if (!arg || !strcmp(arg, "shallow"))
                *thread = THREAD_SHALLOW;
        else if (!strcmp(arg, "deep"))
                *thread = THREAD_DEEP;
        else
                return 1;
        return 0;
}

static int attach_callback(const struct option *opt, const char *arg, int unset)
{
        struct rev_info *rev = (struct rev_info *)opt->value;
        if (unset)
                rev->mime_boundary = NULL;
        else if (arg)
                rev->mime_boundary = arg;
        else
                rev->mime_boundary = git_version_string;
        rev->no_inline = unset ? 0 : 1;
        return 0;
}

static int inline_callback(const struct option *opt, const char *arg, int unset)
{
        struct rev_info *rev = (struct rev_info *)opt->value;
        if (unset)
                rev->mime_boundary = NULL;
        else if (arg)
                rev->mime_boundary = arg;
        else
                rev->mime_boundary = git_version_string;
        rev->no_inline = 0;
        return 0;
}

static int header_callback(const struct option *opt, const char *arg, int unset)
{
        if (unset) {
                string_list_clear(&extra_hdr, 0);
                string_list_clear(&extra_to, 0);
                string_list_clear(&extra_cc, 0);
        } else {
            add_header(arg);
        }
        return 0;
}

static int to_callback(const struct option *opt, const char *arg, int unset)
{
        if (unset)
                string_list_clear(&extra_to, 0);
        else
                string_list_append(&extra_to, arg);
        return 0;
}

static int cc_callback(const struct option *opt, const char *arg, int unset)
{
        if (unset)
                string_list_clear(&extra_cc, 0);
        else
                string_list_append(&extra_cc, arg);
        return 0;
}

static int from_callback(const struct option *opt, const char *arg, int unset)
{
        char **from = opt->value;

        free(*from);

        if (unset)
                *from = NULL;
        else if (arg)
                *from = xstrdup(arg);
        else
                *from = xstrdup(git_committer_info(IDENT_NO_DATE));
        return 0;
}

int cmd_format_patch(int argc, const char **argv, const char *prefix)
{
        struct commit *commit;
        struct commit **list = NULL;
        struct rev_info rev;
        struct setup_revision_opt s_r_opt;
        int nr = 0, total, i;
        int use_stdout = 0;
        int start_number = -1;
        int just_numbers = 0;
        int ignore_if_in_upstream = 0;
        int cover_letter = -1;
        int boundary_count = 0;
        int no_binary_diff = 0;
        int zero_commit = 0;
        struct commit *origin = NULL;
        const char *in_reply_to = NULL;
        struct patch_ids ids;
        struct strbuf buf = STRBUF_INIT;
        int use_patch_format = 0;
        int quiet = 0;
        int reroll_count = -1;
        char *branch_name = NULL;
        char *from = NULL;
        const struct option builtin_format_patch_options[] = {
                { OPTION_CALLBACK, 'n', "numbered", &numbered, NULL,
                            N_("use [PATCH n/m] even with a single patch"),
                            PARSE_OPT_NOARG, numbered_callback },
                { OPTION_CALLBACK, 'N', "no-numbered", &numbered, NULL,
                            N_("use [PATCH] even with multiple patches"),
                            PARSE_OPT_NOARG, no_numbered_callback },
                OPT_BOOL('s', "signoff", &do_signoff, N_("add Signed-off-by:")),
                OPT_BOOL(0, "stdout", &use_stdout,
                            N_("print patches to standard out")),
                OPT_BOOL(0, "cover-letter", &cover_letter,
                            N_("generate a cover letter")),
                OPT_BOOL(0, "numbered-files", &just_numbers,
                            N_("use simple number sequence for output file names")),
                OPT_STRING(0, "suffix", &fmt_patch_suffix, N_("sfx"),
                            N_("use <sfx> instead of '.patch'")),
                OPT_INTEGER(0, "start-number", &start_number,
                            N_("start numbering patches at <n> instead of 1")),
                OPT_INTEGER('v', "reroll-count", &reroll_count,
                            N_("mark the series as Nth re-roll")),
                { OPTION_CALLBACK, 0, "subject-prefix", &rev, N_("prefix"),
                            N_("Use [<prefix>] instead of [PATCH]"),
                            PARSE_OPT_NONEG, subject_prefix_callback },
                { OPTION_CALLBACK, 'o', "output-directory", &output_directory,
                            N_("dir"), N_("store resulting files in <dir>"),
                            PARSE_OPT_NONEG, output_directory_callback },
                { OPTION_CALLBACK, 'k', "keep-subject", &rev, NULL,
                            N_("don't strip/add [PATCH]"),
                            PARSE_OPT_NOARG | PARSE_OPT_NONEG, keep_callback },
                OPT_BOOL(0, "no-binary", &no_binary_diff,
                         N_("don't output binary diffs")),
                OPT_BOOL(0, "zero-commit", &zero_commit,
                         N_("output all-zero hash in From header")),
                OPT_BOOL(0, "ignore-if-in-upstream", &ignore_if_in_upstream,
                         N_("don't include a patch matching a commit upstream")),
                { OPTION_SET_INT, 'p', "no-stat", &use_patch_format, NULL,
                  N_("show patch format instead of default (patch + stat)"),
                  PARSE_OPT_NONEG | PARSE_OPT_NOARG, NULL, 1},
                OPT_GROUP(N_("Messaging")),
                { OPTION_CALLBACK, 0, "add-header", NULL, N_("header"),
                            N_("add email header"), 0, header_callback },
                { OPTION_CALLBACK, 0, "to", NULL, N_("email"), N_("add To: header"),
                            0, to_callback },
                { OPTION_CALLBACK, 0, "cc", NULL, N_("email"), N_("add Cc: header"),
                            0, cc_callback },
                { OPTION_CALLBACK, 0, "from", &from, N_("ident"),
                            N_("set From address to <ident> (or committer ident if absent)"),
                            PARSE_OPT_OPTARG, from_callback },
                OPT_STRING(0, "in-reply-to", &in_reply_to, N_("message-id"),
                            N_("make first mail a reply to <message-id>")),
                { OPTION_CALLBACK, 0, "attach", &rev, N_("boundary"),
                            N_("attach the patch"), PARSE_OPT_OPTARG,
                            attach_callback },
                { OPTION_CALLBACK, 0, "inline", &rev, N_("boundary"),
                            N_("inline the patch"),
                            PARSE_OPT_OPTARG | PARSE_OPT_NONEG,
                            inline_callback },
                { OPTION_CALLBACK, 0, "thread", &thread, N_("style"),
                            N_("enable message threading, styles: shallow, deep"),
                            PARSE_OPT_OPTARG, thread_callback },
                OPT_STRING(0, "signature", &signature, N_("signature"),
                            N_("add a signature")),
                OPT_FILENAME(0, "signature-file", &signature_file,
                                N_("add a signature from a file")),
                OPT__QUIET(&quiet, N_("don't print the patch filenames")),
                OPT_END()
        };

        extra_hdr.strdup_strings = 1;
        extra_to.strdup_strings = 1;
        extra_cc.strdup_strings = 1;
        init_grep_defaults();
        git_config(git_format_config, NULL);
        init_revisions(&rev, prefix);
        rev.commit_format = CMIT_FMT_EMAIL;
        rev.verbose_header = 1;
        rev.diff = 1;
        rev.max_parents = 1;
        DIFF_OPT_SET(&rev.diffopt, RECURSIVE);
        rev.subject_prefix = fmt_patch_subject_prefix;
        memset(&s_r_opt, 0, sizeof(s_r_opt));
        s_r_opt.def = "HEAD";
        s_r_opt.revarg_opt = REVARG_COMMITTISH;

        if (default_attach) {
                rev.mime_boundary = default_attach;
                rev.no_inline = 1;
        }

        /*
         * Parse the arguments before setup_revisions(), or something
         * like "git format-patch -o a123 HEAD^.." may fail; a123 is
         * possibly a valid SHA1.
         */
        argc = parse_options(argc, argv, prefix, builtin_format_patch_options,
                             builtin_format_patch_usage,
                             PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN |
                             PARSE_OPT_KEEP_DASHDASH);

        if (0 < reroll_count) {
                struct strbuf sprefix = STRBUF_INIT;
                strbuf_addf(&sprefix, "%s v%d",
                            rev.subject_prefix, reroll_count);
                rev.reroll_count = reroll_count;
                rev.subject_prefix = strbuf_detach(&sprefix, NULL);
        }

        for (i = 0; i < extra_hdr.nr; i++) {
                strbuf_addstr(&buf, extra_hdr.items[i].string);
                strbuf_addch(&buf, '\n');
        }

        if (extra_to.nr)
                strbuf_addstr(&buf, "To: ");
        for (i = 0; i < extra_to.nr; i++) {
                if (i)
                        strbuf_addstr(&buf, "    ");
                strbuf_addstr(&buf, extra_to.items[i].string);
                if (i + 1 < extra_to.nr)
                        strbuf_addch(&buf, ',');
                strbuf_addch(&buf, '\n');
        }

        if (extra_cc.nr)
                strbuf_addstr(&buf, "Cc: ");
        for (i = 0; i < extra_cc.nr; i++) {
                if (i)
                        strbuf_addstr(&buf, "    ");
                strbuf_addstr(&buf, extra_cc.items[i].string);
                if (i + 1 < extra_cc.nr)
                        strbuf_addch(&buf, ',');
                strbuf_addch(&buf, '\n');
        }

        rev.extra_headers = strbuf_detach(&buf, NULL);

        if (from) {
                if (split_ident_line(&rev.from_ident, from, strlen(from)))
                        die(_("invalid ident line: %s"), from);
        }

        if (start_number < 0)
                start_number = 1;

        /*
         * If numbered is set solely due to format.numbered in config,
         * and it would conflict with --keep-subject (-k) from the
         * command line, reset "numbered".
         */
        if (numbered && keep_subject && !numbered_cmdline_opt)
                numbered = 0;

        if (numbered && keep_subject)
                die (_("-n and -k are mutually exclusive."));
        if (keep_subject && subject_prefix)
                die (_("--subject-prefix and -k are mutually exclusive."));
        rev.preserve_subject = keep_subject;

        argc = setup_revisions(argc, argv, &rev, &s_r_opt);
        if (argc > 1)
                die (_("unrecognized argument: %s"), argv[1]);

        if (rev.diffopt.output_format & DIFF_FORMAT_NAME)
                die(_("--name-only does not make sense"));
        if (rev.diffopt.output_format & DIFF_FORMAT_NAME_STATUS)
                die(_("--name-status does not make sense"));
        if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
                die(_("--check does not make sense"));

        if (!use_patch_format &&
                (!rev.diffopt.output_format ||
                 rev.diffopt.output_format == DIFF_FORMAT_PATCH))
                rev.diffopt.output_format = DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_SUMMARY;

        /* Always generate a patch */
        rev.diffopt.output_format |= DIFF_FORMAT_PATCH;

        rev.zero_commit = zero_commit;

        if (!DIFF_OPT_TST(&rev.diffopt, TEXT) && !no_binary_diff)
                DIFF_OPT_SET(&rev.diffopt, BINARY);

        if (rev.show_notes)
                init_display_notes(&rev.notes_opt);

        if (!use_stdout)
                output_directory = set_outdir(prefix, output_directory);
        else
                setup_pager();

        if (output_directory) {
                if (use_stdout)
                        die(_("standard output, or directory, which one?"));
                if (mkdir(output_directory, 0777) < 0 && errno != EEXIST)
                        die_errno(_("Could not create directory '%s'"),
                                  output_directory);
        }

        if (rev.pending.nr == 1) {
                int check_head = 0;

                if (rev.max_count < 0 && !rev.show_root_diff) {
                        /*
                         * This is traditional behaviour of "git format-patch
                         * origin" that prepares what the origin side still
                         * does not have.
                         */
                        rev.pending.objects[0].item->flags |= UNINTERESTING;
                        add_head_to_pending(&rev);
                        check_head = 1;
                }
                /*
                 * Otherwise, it is "format-patch -22 HEAD", and/or
                 * "format-patch --root HEAD".  The user wants
                 * get_revision() to do the usual traversal.
                 */

                if (!strcmp(rev.pending.objects[0].name, "HEAD"))
                        check_head = 1;

                if (check_head) {
                        unsigned char sha1[20];
                        const char *ref, *v;
                        ref = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING,
                                                 sha1, NULL);
                        if (ref && skip_prefix(ref, "refs/heads/", &v))
                                branch_name = xstrdup(v);
                        else
                                branch_name = xstrdup(""); /* no branch */
                }
        }

        /*
         * We cannot move this anywhere earlier because we do want to
         * know if --root was given explicitly from the command line.
         */
        rev.show_root_diff = 1;

        if (ignore_if_in_upstream) {
                /* Don't say anything if head and upstream are the same. */
                if (rev.pending.nr == 2) {
                        struct object_array_entry *o = rev.pending.objects;
                        if (oidcmp(&o[0].item->oid, &o[1].item->oid) == 0)
                                return 0;
                }
                get_patch_ids(&rev, &ids);
        }

        if (!use_stdout)
                realstdout = xfdopen(xdup(1), "w");

        if (prepare_revision_walk(&rev))
                die(_("revision walk setup failed"));
        rev.boundary = 1;
        while ((commit = get_revision(&rev)) != NULL) {
                if (commit->object.flags & BOUNDARY) {
                        boundary_count++;
                        origin = (boundary_count == 1) ? commit : NULL;
                        continue;
                }

                if (ignore_if_in_upstream && has_commit_patch_id(commit, &ids))
                        continue;

                nr++;
                REALLOC_ARRAY(list, nr);
                list[nr - 1] = commit;
        }
        if (nr == 0)
                /* nothing to do */
                return 0;
        total = nr;
        if (!keep_subject && auto_number && total > 1)
                numbered = 1;
        if (numbered)
                rev.total = total + start_number - 1;
        if (cover_letter == -1) {
                if (config_cover_letter == COVER_AUTO)
                        cover_letter = (total > 1);
                else
                        cover_letter = (config_cover_letter == COVER_ON);
        }

        if (!signature) {
                ; /* --no-signature inhibits all signatures */
        } else if (signature && signature != git_version_string) {
                ; /* non-default signature already set */
        } else if (signature_file) {
                struct strbuf buf = STRBUF_INIT;

                if (strbuf_read_file(&buf, signature_file, 128) < 0)
                        die_errno(_("unable to read signature file '%s'"), signature_file);
                signature = strbuf_detach(&buf, NULL);
        }

        if (in_reply_to || thread || cover_letter)
                rev.ref_message_ids = xcalloc(1, sizeof(struct string_list));
        if (in_reply_to) {
                const char *msgid = clean_message_id(in_reply_to);
                string_list_append(rev.ref_message_ids, msgid);
        }
        rev.numbered_files = just_numbers;
        rev.patch_suffix = fmt_patch_suffix;
        if (cover_letter) {
                if (thread)
                        gen_message_id(&rev, "cover");
                make_cover_letter(&rev, use_stdout,
                                  origin, nr, list, branch_name, quiet);
                total++;
                start_number--;
        }
        rev.add_signoff = do_signoff;
        while (0 <= --nr) {
                int shown;
                commit = list[nr];
                rev.nr = total - nr + (start_number - 1);
                /* Make the second and subsequent mails replies to the first */
                if (thread) {
                        /* Have we already had a message ID? */
                        if (rev.message_id) {
                                /*
                                 * For deep threading: make every mail
                                 * a reply to the previous one, no
                                 * matter what other options are set.
                                 *
                                 * For shallow threading:
                                 *
                                 * Without --cover-letter and
                                 * --in-reply-to, make every mail a
                                 * reply to the one before.
                                 *
                                 * With --in-reply-to but no
                                 * --cover-letter, make every mail a
                                 * reply to the <reply-to>.
                                 *
                                 * With --cover-letter, make every
                                 * mail but the cover letter a reply
                                 * to the cover letter.  The cover
                                 * letter is a reply to the
                                 * --in-reply-to, if specified.
                                 */
                                if (thread == THREAD_SHALLOW
                                    && rev.ref_message_ids->nr > 0
                                    && (!cover_letter || rev.nr > 1))
                                        free(rev.message_id);
                                else
                                        string_list_append(rev.ref_message_ids,
                                                           rev.message_id);
                        }
                        gen_message_id(&rev, oid_to_hex(&commit->object.oid));
                }

                if (!use_stdout &&
                    reopen_stdout(rev.numbered_files ? NULL : commit, NULL, &rev, quiet))
                        die(_("Failed to create output files"));
                shown = log_tree_commit(&rev, commit);
                free_commit_buffer(commit);

                /* We put one extra blank line between formatted
                 * patches and this flag is used by log-tree code
                 * to see if it needs to emit a LF before showing
                 * the log; when using one file per patch, we do
                 * not want the extra blank line.
                 */
                if (!use_stdout)
                        rev.shown_one = 0;
                if (shown) {
                        if (rev.mime_boundary)
                                printf("\n--%s%s--\n\n\n",
                                       mime_boundary_leader,
                                       rev.mime_boundary);
                        else
                                print_signature();
                }
                if (!use_stdout)
                        fclose(stdout);
        }
        free(list);
        free(branch_name);
        string_list_clear(&extra_to, 0);
        string_list_clear(&extra_cc, 0);
        string_list_clear(&extra_hdr, 0);
        if (ignore_if_in_upstream)
                free_patch_ids(&ids);
        return 0;
}

static int add_pending_commit(const char *arg, struct rev_info *revs, int flags)
{
        unsigned char sha1[20];
        if (get_sha1(arg, sha1) == 0) {
                struct commit *commit = lookup_commit_reference(sha1);
                if (commit) {
                        commit->object.flags |= flags;
                        add_pending_object(revs, &commit->object, arg);
                        return 0;
                }
        }
        return -1;
}

static const char * const cherry_usage[] = {
        N_("git cherry [-v] [<upstream> [<head> [<limit>]]]"),
        NULL
};

static void print_commit(char sign, struct commit *commit, int verbose,
                         int abbrev)
{
        if (!verbose) {
                printf("%c %s\n", sign,
                       find_unique_abbrev(commit->object.oid.hash, abbrev));
        } else {
                struct strbuf buf = STRBUF_INIT;
                pp_commit_easy(CMIT_FMT_ONELINE, commit, &buf);
                printf("%c %s %s\n", sign,
                       find_unique_abbrev(commit->object.oid.hash, abbrev),
                       buf.buf);
                strbuf_release(&buf);
        }
}

int cmd_cherry(int argc, const char **argv, const char *prefix)
{
        struct rev_info revs;
        struct patch_ids ids;
        struct commit *commit;
        struct commit_list *list = NULL;
        struct branch *current_branch;
        const char *upstream;
        const char *head = "HEAD";
        const char *limit = NULL;
        int verbose = 0, abbrev = 0;

        struct option options[] = {
                OPT__ABBREV(&abbrev),
                OPT__VERBOSE(&verbose, N_("be verbose")),
                OPT_END()
        };

        argc = parse_options(argc, argv, prefix, options, cherry_usage, 0);

        switch (argc) {
        case 3:
                limit = argv[2];
                /* FALLTHROUGH */
        case 2:
                head = argv[1];
                /* FALLTHROUGH */
        case 1:
                upstream = argv[0];
                break;
        default:
                current_branch = branch_get(NULL);
                upstream = branch_get_upstream(current_branch, NULL);
                if (!upstream) {
                        fprintf(stderr, _("Could not find a tracked"
                                        " remote branch, please"
                                        " specify <upstream> manually.\n"));
                        usage_with_options(cherry_usage, options);
                }
        }

        init_revisions(&revs, prefix);
        revs.max_parents = 1;

        if (add_pending_commit(head, &revs, 0))
                die(_("Unknown commit %s"), head);
        if (add_pending_commit(upstream, &revs, UNINTERESTING))
                die(_("Unknown commit %s"), upstream);

        /* Don't say anything if head and upstream are the same. */
        if (revs.pending.nr == 2) {
                struct object_array_entry *o = revs.pending.objects;
                if (oidcmp(&o[0].item->oid, &o[1].item->oid) == 0)
                        return 0;
        }

        get_patch_ids(&revs, &ids);

        if (limit && add_pending_commit(limit, &revs, UNINTERESTING))
                die(_("Unknown commit %s"), limit);

        /* reverse the list of commits */
        if (prepare_revision_walk(&revs))
                die(_("revision walk setup failed"));
        while ((commit = get_revision(&revs)) != NULL) {
                commit_list_insert(commit, &list);
        }

        while (list) {
                char sign = '+';

                commit = list->item;
                if (has_commit_patch_id(commit, &ids))
                        sign = '-';
                print_commit(sign, commit, verbose, abbrev);
                list = list->next;
        }

        free_patch_ids(&ids);
        return 0;
}