sha1_name: make wraparound of the index into ring-buffer explicit

[git.git] / trailer.c

#include "cache.h"
#include "string-list.h"
#include "run-command.h"
#include "commit.h"
#include "tempfile.h"
#include "trailer.h"
/*
 * Copyright (c) 2013, 2014 Christian Couder <chriscool@tuxfamily.org>
 */

enum action_where { WHERE_END, WHERE_AFTER, WHERE_BEFORE, WHERE_START };
enum action_if_exists { EXISTS_ADD_IF_DIFFERENT_NEIGHBOR, EXISTS_ADD_IF_DIFFERENT,
                        EXISTS_ADD, EXISTS_REPLACE, EXISTS_DO_NOTHING };
enum action_if_missing { MISSING_ADD, MISSING_DO_NOTHING };

struct conf_info {
        char *name;
        char *key;
        char *command;
        enum action_where where;
        enum action_if_exists if_exists;
        enum action_if_missing if_missing;
};

static struct conf_info default_conf_info;

struct trailer_item {
        struct trailer_item *previous;
        struct trailer_item *next;
        const char *token;
        const char *value;
        struct conf_info conf;
};

static struct trailer_item *first_conf_item;

static char *separators = ":";

#define TRAILER_ARG_STRING "$ARG"

static int after_or_end(enum action_where where)
{
        return (where == WHERE_AFTER) || (where == WHERE_END);
}

/*
 * Return the length of the string not including any final
 * punctuation. E.g., the input "Signed-off-by:" would return
 * 13, stripping the trailing punctuation but retaining
 * internal punctuation.
 */
static size_t token_len_without_separator(const char *token, size_t len)
{
        while (len > 0 && !isalnum(token[len - 1]))
                len--;
        return len;
}

static int same_token(struct trailer_item *a, struct trailer_item *b)
{
        size_t a_len = token_len_without_separator(a->token, strlen(a->token));
        size_t b_len = token_len_without_separator(b->token, strlen(b->token));
        size_t min_len = (a_len > b_len) ? b_len : a_len;

        return !strncasecmp(a->token, b->token, min_len);
}

static int same_value(struct trailer_item *a, struct trailer_item *b)
{
        return !strcasecmp(a->value, b->value);
}

static int same_trailer(struct trailer_item *a, struct trailer_item *b)
{
        return same_token(a, b) && same_value(a, b);
}

static inline int contains_only_spaces(const char *str)
{
        const char *s = str;
        while (*s && isspace(*s))
                s++;
        return !*s;
}

static inline void strbuf_replace(struct strbuf *sb, const char *a, const char *b)
{
        const char *ptr = strstr(sb->buf, a);
        if (ptr)
                strbuf_splice(sb, ptr - sb->buf, strlen(a), b, strlen(b));
}

static void free_trailer_item(struct trailer_item *item)
{
        free(item->conf.name);
        free(item->conf.key);
        free(item->conf.command);
        free((char *)item->token);
        free((char *)item->value);
        free(item);
}

static char last_non_space_char(const char *s)
{
        int i;
        for (i = strlen(s) - 1; i >= 0; i--)
                if (!isspace(s[i]))
                        return s[i];
        return '\0';
}

static void print_tok_val(FILE *outfile, const char *tok, const char *val)
{
        char c = last_non_space_char(tok);
        if (!c)
                return;
        if (strchr(separators, c))
                fprintf(outfile, "%s%s\n", tok, val);
        else
                fprintf(outfile, "%s%c %s\n", tok, separators[0], val);
}

static void print_all(FILE *outfile, struct trailer_item *first, int trim_empty)
{
        struct trailer_item *item;
        for (item = first; item; item = item->next) {
                if (!trim_empty || strlen(item->value) > 0)
                        print_tok_val(outfile, item->token, item->value);
        }
}

static void update_last(struct trailer_item **last)
{
        if (*last)
                while ((*last)->next != NULL)
                        *last = (*last)->next;
}

static void update_first(struct trailer_item **first)
{
        if (*first)
                while ((*first)->previous != NULL)
                        *first = (*first)->previous;
}

static void add_arg_to_input_list(struct trailer_item *on_tok,
                                  struct trailer_item *arg_tok,
                                  struct trailer_item **first,
                                  struct trailer_item **last)
{
        if (after_or_end(arg_tok->conf.where)) {
                arg_tok->next = on_tok->next;
                on_tok->next = arg_tok;
                arg_tok->previous = on_tok;
                if (arg_tok->next)
                        arg_tok->next->previous = arg_tok;
                update_last(last);
        } else {
                arg_tok->previous = on_tok->previous;
                on_tok->previous = arg_tok;
                arg_tok->next = on_tok;
                if (arg_tok->previous)
                        arg_tok->previous->next = arg_tok;
                update_first(first);
        }
}

static int check_if_different(struct trailer_item *in_tok,
                              struct trailer_item *arg_tok,
                              int check_all)
{
        enum action_where where = arg_tok->conf.where;
        do {
                if (!in_tok)
                        return 1;
                if (same_trailer(in_tok, arg_tok))
                        return 0;
                /*
                 * if we want to add a trailer after another one,
                 * we have to check those before this one
                 */
                in_tok = after_or_end(where) ? in_tok->previous : in_tok->next;
        } while (check_all);
        return 1;
}

static void remove_from_list(struct trailer_item *item,
                             struct trailer_item **first,
                             struct trailer_item **last)
{
        struct trailer_item *next = item->next;
        struct trailer_item *previous = item->previous;

        if (next) {
                item->next->previous = previous;
                item->next = NULL;
        } else if (last)
                *last = previous;

        if (previous) {
                item->previous->next = next;
                item->previous = NULL;
        } else if (first)
                *first = next;
}

static struct trailer_item *remove_first(struct trailer_item **first)
{
        struct trailer_item *item = *first;
        *first = item->next;
        if (item->next) {
                item->next->previous = NULL;
                item->next = NULL;
        }
        return item;
}

static const char *apply_command(const char *command, const char *arg)
{
        struct strbuf cmd = STRBUF_INIT;
        struct strbuf buf = STRBUF_INIT;
        struct child_process cp = CHILD_PROCESS_INIT;
        const char *argv[] = {NULL, NULL};
        const char *result;

        strbuf_addstr(&cmd, command);
        if (arg)
                strbuf_replace(&cmd, TRAILER_ARG_STRING, arg);

        argv[0] = cmd.buf;
        cp.argv = argv;
        cp.env = local_repo_env;
        cp.no_stdin = 1;
        cp.use_shell = 1;

        if (capture_command(&cp, &buf, 1024)) {
                error(_("running trailer command '%s' failed"), cmd.buf);
                strbuf_release(&buf);
                result = xstrdup("");
        } else {
                strbuf_trim(&buf);
                result = strbuf_detach(&buf, NULL);
        }

        strbuf_release(&cmd);
        return result;
}

static void apply_item_command(struct trailer_item *in_tok, struct trailer_item *arg_tok)
{
        if (arg_tok->conf.command) {
                const char *arg;
                if (arg_tok->value && arg_tok->value[0]) {
                        arg = arg_tok->value;
                } else {
                        if (in_tok && in_tok->value)
                                arg = xstrdup(in_tok->value);
                        else
                                arg = xstrdup("");
                }
                arg_tok->value = apply_command(arg_tok->conf.command, arg);
                free((char *)arg);
        }
}

static void apply_arg_if_exists(struct trailer_item *in_tok,
                                struct trailer_item *arg_tok,
                                struct trailer_item *on_tok,
                                struct trailer_item **in_tok_first,
                                struct trailer_item **in_tok_last)
{
        switch (arg_tok->conf.if_exists) {
        case EXISTS_DO_NOTHING:
                free_trailer_item(arg_tok);
                break;
        case EXISTS_REPLACE:
                apply_item_command(in_tok, arg_tok);
                add_arg_to_input_list(on_tok, arg_tok,
                                      in_tok_first, in_tok_last);
                remove_from_list(in_tok, in_tok_first, in_tok_last);
                free_trailer_item(in_tok);
                break;
        case EXISTS_ADD:
                apply_item_command(in_tok, arg_tok);
                add_arg_to_input_list(on_tok, arg_tok,
                                      in_tok_first, in_tok_last);
                break;
        case EXISTS_ADD_IF_DIFFERENT:
                apply_item_command(in_tok, arg_tok);
                if (check_if_different(in_tok, arg_tok, 1))
                        add_arg_to_input_list(on_tok, arg_tok,
                                              in_tok_first, in_tok_last);
                else
                        free_trailer_item(arg_tok);
                break;
        case EXISTS_ADD_IF_DIFFERENT_NEIGHBOR:
                apply_item_command(in_tok, arg_tok);
                if (check_if_different(on_tok, arg_tok, 0))
                        add_arg_to_input_list(on_tok, arg_tok,
                                              in_tok_first, in_tok_last);
                else
                        free_trailer_item(arg_tok);
                break;
        }
}

static void apply_arg_if_missing(struct trailer_item **in_tok_first,
                                 struct trailer_item **in_tok_last,
                                 struct trailer_item *arg_tok)
{
        struct trailer_item **in_tok;
        enum action_where where;

        switch (arg_tok->conf.if_missing) {
        case MISSING_DO_NOTHING:
                free_trailer_item(arg_tok);
                break;
        case MISSING_ADD:
                where = arg_tok->conf.where;
                in_tok = after_or_end(where) ? in_tok_last : in_tok_first;
                apply_item_command(NULL, arg_tok);
                if (*in_tok) {
                        add_arg_to_input_list(*in_tok, arg_tok,
                                              in_tok_first, in_tok_last);
                } else {
                        *in_tok_first = arg_tok;
                        *in_tok_last = arg_tok;
                }
                break;
        }
}

static int find_same_and_apply_arg(struct trailer_item **in_tok_first,
                                   struct trailer_item **in_tok_last,
                                   struct trailer_item *arg_tok)
{
        struct trailer_item *in_tok;
        struct trailer_item *on_tok;
        struct trailer_item *following_tok;

        enum action_where where = arg_tok->conf.where;
        int middle = (where == WHERE_AFTER) || (where == WHERE_BEFORE);
        int backwards = after_or_end(where);
        struct trailer_item *start_tok = backwards ? *in_tok_last : *in_tok_first;

        for (in_tok = start_tok; in_tok; in_tok = following_tok) {
                following_tok = backwards ? in_tok->previous : in_tok->next;
                if (!same_token(in_tok, arg_tok))
                        continue;
                on_tok = middle ? in_tok : start_tok;
                apply_arg_if_exists(in_tok, arg_tok, on_tok,
                                    in_tok_first, in_tok_last);
                return 1;
        }
        return 0;
}

static void process_trailers_lists(struct trailer_item **in_tok_first,
                                   struct trailer_item **in_tok_last,
                                   struct trailer_item **arg_tok_first)
{
        struct trailer_item *arg_tok;
        struct trailer_item *next_arg;

        if (!*arg_tok_first)
                return;

        for (arg_tok = *arg_tok_first; arg_tok; arg_tok = next_arg) {
                int applied = 0;

                next_arg = arg_tok->next;
                remove_from_list(arg_tok, arg_tok_first, NULL);

                applied = find_same_and_apply_arg(in_tok_first,
                                                  in_tok_last,
                                                  arg_tok);

                if (!applied)
                        apply_arg_if_missing(in_tok_first,
                                             in_tok_last,
                                             arg_tok);
        }
}

static int set_where(struct conf_info *item, const char *value)
{
        if (!strcasecmp("after", value))
                item->where = WHERE_AFTER;
        else if (!strcasecmp("before", value))
                item->where = WHERE_BEFORE;
        else if (!strcasecmp("end", value))
                item->where = WHERE_END;
        else if (!strcasecmp("start", value))
                item->where = WHERE_START;
        else
                return -1;
        return 0;
}

static int set_if_exists(struct conf_info *item, const char *value)
{
        if (!strcasecmp("addIfDifferent", value))
                item->if_exists = EXISTS_ADD_IF_DIFFERENT;
        else if (!strcasecmp("addIfDifferentNeighbor", value))
                item->if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
        else if (!strcasecmp("add", value))
                item->if_exists = EXISTS_ADD;
        else if (!strcasecmp("replace", value))
                item->if_exists = EXISTS_REPLACE;
        else if (!strcasecmp("doNothing", value))
                item->if_exists = EXISTS_DO_NOTHING;
        else
                return -1;
        return 0;
}

static int set_if_missing(struct conf_info *item, const char *value)
{
        if (!strcasecmp("doNothing", value))
                item->if_missing = MISSING_DO_NOTHING;
        else if (!strcasecmp("add", value))
                item->if_missing = MISSING_ADD;
        else
                return -1;
        return 0;
}

static void duplicate_conf(struct conf_info *dst, struct conf_info *src)
{
        *dst = *src;
        dst->name = xstrdup_or_null(src->name);
        dst->key = xstrdup_or_null(src->key);
        dst->command = xstrdup_or_null(src->command);
}

static struct trailer_item *get_conf_item(const char *name)
{
        struct trailer_item *item;
        struct trailer_item *previous;

        /* Look up item with same name */
        for (previous = NULL, item = first_conf_item;
             item;
             previous = item, item = item->next) {
                if (!strcasecmp(item->conf.name, name))
                        return item;
        }

        /* Item does not already exists, create it */
        item = xcalloc(sizeof(struct trailer_item), 1);
        duplicate_conf(&item->conf, &default_conf_info);
        item->conf.name = xstrdup(name);

        if (!previous)
                first_conf_item = item;
        else {
                previous->next = item;
                item->previous = previous;
        }

        return item;
}

enum trailer_info_type { TRAILER_KEY, TRAILER_COMMAND, TRAILER_WHERE,
                         TRAILER_IF_EXISTS, TRAILER_IF_MISSING };

static struct {
        const char *name;
        enum trailer_info_type type;
} trailer_config_items[] = {
        { "key", TRAILER_KEY },
        { "command", TRAILER_COMMAND },
        { "where", TRAILER_WHERE },
        { "ifexists", TRAILER_IF_EXISTS },
        { "ifmissing", TRAILER_IF_MISSING }
};

static int git_trailer_default_config(const char *conf_key, const char *value, void *cb)
{
        const char *trailer_item, *variable_name;

        if (!skip_prefix(conf_key, "trailer.", &trailer_item))
                return 0;

        variable_name = strrchr(trailer_item, '.');
        if (!variable_name) {
                if (!strcmp(trailer_item, "where")) {
                        if (set_where(&default_conf_info, value) < 0)
                                warning(_("unknown value '%s' for key '%s'"),
                                        value, conf_key);
                } else if (!strcmp(trailer_item, "ifexists")) {
                        if (set_if_exists(&default_conf_info, value) < 0)
                                warning(_("unknown value '%s' for key '%s'"),
                                        value, conf_key);
                } else if (!strcmp(trailer_item, "ifmissing")) {
                        if (set_if_missing(&default_conf_info, value) < 0)
                                warning(_("unknown value '%s' for key '%s'"),
                                        value, conf_key);
                } else if (!strcmp(trailer_item, "separators")) {
                        separators = xstrdup(value);
                }
        }
        return 0;
}

static int git_trailer_config(const char *conf_key, const char *value, void *cb)
{
        const char *trailer_item, *variable_name;
        struct trailer_item *item;
        struct conf_info *conf;
        char *name = NULL;
        enum trailer_info_type type;
        int i;

        if (!skip_prefix(conf_key, "trailer.", &trailer_item))
                return 0;

        variable_name = strrchr(trailer_item, '.');
        if (!variable_name)
                return 0;

        variable_name++;
        for (i = 0; i < ARRAY_SIZE(trailer_config_items); i++) {
                if (strcmp(trailer_config_items[i].name, variable_name))
                        continue;
                name = xstrndup(trailer_item,  variable_name - trailer_item - 1);
                type = trailer_config_items[i].type;
                break;
        }

        if (!name)
                return 0;

        item = get_conf_item(name);
        conf = &item->conf;
        free(name);

        switch (type) {
        case TRAILER_KEY:
                if (conf->key)
                        warning(_("more than one %s"), conf_key);
                conf->key = xstrdup(value);
                break;
        case TRAILER_COMMAND:
                if (conf->command)
                        warning(_("more than one %s"), conf_key);
                conf->command = xstrdup(value);
                break;
        case TRAILER_WHERE:
                if (set_where(conf, value))
                        warning(_("unknown value '%s' for key '%s'"), value, conf_key);
                break;
        case TRAILER_IF_EXISTS:
                if (set_if_exists(conf, value))
                        warning(_("unknown value '%s' for key '%s'"), value, conf_key);
                break;
        case TRAILER_IF_MISSING:
                if (set_if_missing(conf, value))
                        warning(_("unknown value '%s' for key '%s'"), value, conf_key);
                break;
        default:
                die("BUG: trailer.c: unhandled type %d", type);
        }
        return 0;
}

static int parse_trailer(struct strbuf *tok, struct strbuf *val, const char *trailer)
{
        size_t len;
        struct strbuf seps = STRBUF_INIT;
        strbuf_addstr(&seps, separators);
        strbuf_addch(&seps, '=');
        len = strcspn(trailer, seps.buf);
        strbuf_release(&seps);
        if (len == 0) {
                int l = strlen(trailer);
                while (l > 0 && isspace(trailer[l - 1]))
                        l--;
                return error(_("empty trailer token in trailer '%.*s'"), l, trailer);
        }
        if (len < strlen(trailer)) {
                strbuf_add(tok, trailer, len);
                strbuf_trim(tok);
                strbuf_addstr(val, trailer + len + 1);
                strbuf_trim(val);
        } else {
                strbuf_addstr(tok, trailer);
                strbuf_trim(tok);
        }
        return 0;
}

static const char *token_from_item(struct trailer_item *item, char *tok)
{
        if (item->conf.key)
                return item->conf.key;
        if (tok)
                return tok;
        return item->conf.name;
}

static struct trailer_item *new_trailer_item(struct trailer_item *conf_item,
                                             char *tok, char *val)
{
        struct trailer_item *new = xcalloc(sizeof(*new), 1);
        new->value = val ? val : xstrdup("");

        if (conf_item) {
                duplicate_conf(&new->conf, &conf_item->conf);
                new->token = xstrdup(token_from_item(conf_item, tok));
                free(tok);
        } else {
                duplicate_conf(&new->conf, &default_conf_info);
                new->token = tok;
        }

        return new;
}

static int token_matches_item(const char *tok, struct trailer_item *item, int tok_len)
{
        if (!strncasecmp(tok, item->conf.name, tok_len))
                return 1;
        return item->conf.key ? !strncasecmp(tok, item->conf.key, tok_len) : 0;
}

static struct trailer_item *create_trailer_item(const char *string)
{
        struct strbuf tok = STRBUF_INIT;
        struct strbuf val = STRBUF_INIT;
        struct trailer_item *item;
        int tok_len;

        if (parse_trailer(&tok, &val, string))
                return NULL;

        tok_len = token_len_without_separator(tok.buf, tok.len);

        /* Lookup if the token matches something in the config */
        for (item = first_conf_item; item; item = item->next) {
                if (token_matches_item(tok.buf, item, tok_len))
                        return new_trailer_item(item,
                                                strbuf_detach(&tok, NULL),
                                                strbuf_detach(&val, NULL));
        }

        return new_trailer_item(NULL,
                                strbuf_detach(&tok, NULL),
                                strbuf_detach(&val, NULL));
}

static void add_trailer_item(struct trailer_item **first,
                             struct trailer_item **last,
                             struct trailer_item *new)
{
        if (!new)
                return;
        if (!*last) {
                *first = new;
                *last = new;
        } else {
                (*last)->next = new;
                new->previous = *last;
                *last = new;
        }
}

static struct trailer_item *process_command_line_args(struct string_list *trailers)
{
        struct trailer_item *arg_tok_first = NULL;
        struct trailer_item *arg_tok_last = NULL;
        struct string_list_item *tr;
        struct trailer_item *item;

        /* Add a trailer item for each configured trailer with a command */
        for (item = first_conf_item; item; item = item->next) {
                if (item->conf.command) {
                        struct trailer_item *new = new_trailer_item(item, NULL, NULL);
                        add_trailer_item(&arg_tok_first, &arg_tok_last, new);
                }
        }

        /* Add a trailer item for each trailer on the command line */
        for_each_string_list_item(tr, trailers) {
                struct trailer_item *new = create_trailer_item(tr->string);
                add_trailer_item(&arg_tok_first, &arg_tok_last, new);
        }

        return arg_tok_first;
}

static struct strbuf **read_input_file(const char *file)
{
        struct strbuf **lines;
        struct strbuf sb = STRBUF_INIT;

        if (file) {
                if (strbuf_read_file(&sb, file, 0) < 0)
                        die_errno(_("could not read input file '%s'"), file);
        } else {
                if (strbuf_read(&sb, fileno(stdin), 0) < 0)
                        die_errno(_("could not read from stdin"));
        }

        lines = strbuf_split(&sb, '\n');

        strbuf_release(&sb);

        return lines;
}

/*
 * Return the (0 based) index of the start of the patch or the line
 * count if there is no patch in the message.
 */
static int find_patch_start(struct strbuf **lines, int count)
{
        int i;

        /* Get the start of the patch part if any */
        for (i = 0; i < count; i++) {
                if (starts_with(lines[i]->buf, "---"))
                        return i;
        }

        return count;
}

/*
 * Return the (0 based) index of the first trailer line or count if
 * there are no trailers. Trailers are searched only in the lines from
 * index (count - 1) down to index 0.
 */
static int find_trailer_start(struct strbuf **lines, int count)
{
        int start, end_of_title, only_spaces = 1;

        /* The first paragraph is the title and cannot be trailers */
        for (start = 0; start < count; start++) {
                if (lines[start]->buf[0] == comment_line_char)
                        continue;
                if (contains_only_spaces(lines[start]->buf))
                        break;
        }
        end_of_title = start;

        /*
         * Get the start of the trailers by looking starting from the end
         * for a line with only spaces before lines with one separator.
         */
        for (start = count - 1; start >= end_of_title; start--) {
                if (lines[start]->buf[0] == comment_line_char)
                        continue;
                if (contains_only_spaces(lines[start]->buf)) {
                        if (only_spaces)
                                continue;
                        return start + 1;
                }
                if (strcspn(lines[start]->buf, separators) < lines[start]->len) {
                        if (only_spaces)
                                only_spaces = 0;
                        continue;
                }
                return count;
        }

        return only_spaces ? count : 0;
}

/* Get the index of the end of the trailers */
static int find_trailer_end(struct strbuf **lines, int patch_start)
{
        struct strbuf sb = STRBUF_INIT;
        int i, ignore_bytes;

        for (i = 0; i < patch_start; i++)
                strbuf_addbuf(&sb, lines[i]);
        ignore_bytes = ignore_non_trailer(&sb);
        strbuf_release(&sb);
        for (i = patch_start - 1; i >= 0 && ignore_bytes > 0; i--)
                ignore_bytes -= lines[i]->len;

        return i + 1;
}

static int has_blank_line_before(struct strbuf **lines, int start)
{
        for (;start >= 0; start--) {
                if (lines[start]->buf[0] == comment_line_char)
                        continue;
                return contains_only_spaces(lines[start]->buf);
        }
        return 0;
}

static void print_lines(FILE *outfile, struct strbuf **lines, int start, int end)
{
        int i;
        for (i = start; lines[i] && i < end; i++)
                fprintf(outfile, "%s", lines[i]->buf);
}

static int process_input_file(FILE *outfile,
                              struct strbuf **lines,
                              struct trailer_item **in_tok_first,
                              struct trailer_item **in_tok_last)
{
        int count = 0;
        int patch_start, trailer_start, trailer_end, i;

        /* Get the line count */
        while (lines[count])
                count++;

        patch_start = find_patch_start(lines, count);
        trailer_end = find_trailer_end(lines, patch_start);
        trailer_start = find_trailer_start(lines, trailer_end);

        /* Print lines before the trailers as is */
        print_lines(outfile, lines, 0, trailer_start);

        if (!has_blank_line_before(lines, trailer_start - 1))
                fprintf(outfile, "\n");

        /* Parse trailer lines */
        for (i = trailer_start; i < trailer_end; i++) {
                if (lines[i]->buf[0] != comment_line_char) {
                        struct trailer_item *new = create_trailer_item(lines[i]->buf);
                        add_trailer_item(in_tok_first, in_tok_last, new);
                }
        }

        return trailer_end;
}

static void free_all(struct trailer_item **first)
{
        while (*first) {
                struct trailer_item *item = remove_first(first);
                free_trailer_item(item);
        }
}

static struct tempfile trailers_tempfile;

static FILE *create_in_place_tempfile(const char *file)
{
        struct stat st;
        struct strbuf template = STRBUF_INIT;
        const char *tail;
        FILE *outfile;

        if (stat(file, &st))
                die_errno(_("could not stat %s"), file);
        if (!S_ISREG(st.st_mode))
                die(_("file %s is not a regular file"), file);
        if (!(st.st_mode & S_IWUSR))
                die(_("file %s is not writable by user"), file);

        /* Create temporary file in the same directory as the original */
        tail = strrchr(file, '/');
        if (tail != NULL)
                strbuf_add(&template, file, tail - file + 1);
        strbuf_addstr(&template, "git-interpret-trailers-XXXXXX");

        xmks_tempfile_m(&trailers_tempfile, template.buf, st.st_mode);
        strbuf_release(&template);
        outfile = fdopen_tempfile(&trailers_tempfile, "w");
        if (!outfile)
                die_errno(_("could not open temporary file"));

        return outfile;
}

void process_trailers(const char *file, int in_place, int trim_empty, struct string_list *trailers)
{
        struct trailer_item *in_tok_first = NULL;
        struct trailer_item *in_tok_last = NULL;
        struct trailer_item *arg_tok_first;
        struct strbuf **lines;
        int trailer_end;
        FILE *outfile = stdout;

        /* Default config must be setup first */
        git_config(git_trailer_default_config, NULL);
        git_config(git_trailer_config, NULL);

        lines = read_input_file(file);

        if (in_place)
                outfile = create_in_place_tempfile(file);

        /* Print the lines before the trailers */
        trailer_end = process_input_file(outfile, lines, &in_tok_first, &in_tok_last);

        arg_tok_first = process_command_line_args(trailers);

        process_trailers_lists(&in_tok_first, &in_tok_last, &arg_tok_first);

        print_all(outfile, in_tok_first, trim_empty);

        free_all(&in_tok_first);

        /* Print the lines after the trailers as is */
        print_lines(outfile, lines, trailer_end, INT_MAX);

        if (in_place)
                if (rename_tempfile(&trailers_tempfile, file))
                        die_errno(_("could not rename temporary file to %s"), file);

        strbuf_list_free(lines);
}