hash: move SHA-1 macros to hash.h
[gitweb.git] / trailer.c
index aecaf9232a92fcab4996037fc779e0165750fb36..3ba157ed0d6157281f0a9e91f7b7f208652adfcc 100644 (file)
--- a/trailer.c
+++ b/trailer.c
@@ -1,44 +1,64 @@
 #include "cache.h"
+#include "config.h"
 #include "string-list.h"
 #include "run-command.h"
 #include "commit.h"
 #include "tempfile.h"
 #include "trailer.h"
+#include "list.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;
+       enum trailer_where where;
+       enum trailer_if_exists if_exists;
+       enum trailer_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 list_head list;
+       /*
+        * If this is not a trailer line, the line is stored in value
+        * (excluding the terminating newline) and token is NULL.
+        */
+       char *token;
+       char *value;
+};
+
+struct arg_item {
+       struct list_head list;
+       char *token;
+       char *value;
        struct conf_info conf;
 };
 
-static struct trailer_item *first_conf_item;
+static LIST_HEAD(conf_head);
 
 static char *separators = ":";
 
+static int configured;
+
 #define TRAILER_ARG_STRING "$ARG"
 
-static int after_or_end(enum action_where where)
+static const char *git_generated_prefixes[] = {
+       "Signed-off-by: ",
+       "(cherry picked from commit ",
+       NULL
+};
+
+/* Iterate over the elements of the list. */
+#define list_for_each_dir(pos, head, is_reverse) \
+       for (pos = is_reverse ? (head)->prev : (head)->next; \
+               pos != (head); \
+               pos = is_reverse ? pos->prev : pos->next)
+
+static int after_or_end(enum trailer_where where)
 {
        return (where == WHERE_AFTER) || (where == WHERE_END);
 }
@@ -56,31 +76,36 @@ static size_t token_len_without_separator(const char *token, size_t len)
        return len;
 }
 
-static int same_token(struct trailer_item *a, struct trailer_item *b)
+static int same_token(struct trailer_item *a, struct arg_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;
+       size_t a_len, b_len, min_len;
+
+       if (!a->token)
+               return 0;
+
+       a_len = token_len_without_separator(a->token, strlen(a->token));
+       b_len = token_len_without_separator(b->token, strlen(b->token));
+       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)
+static int same_value(struct trailer_item *a, struct arg_item *b)
 {
        return !strcasecmp(a->value, b->value);
 }
 
-static int same_trailer(struct trailer_item *a, struct trailer_item *b)
+static int same_trailer(struct trailer_item *a, struct arg_item *b)
 {
        return same_token(a, b) && same_value(a, b);
 }
 
-static inline int contains_only_spaces(const char *str)
+static inline int is_blank_line(const char *str)
 {
        const char *s = str;
-       while (*s && isspace(*s))
+       while (*s && *s != '\n' && isspace(*s))
                s++;
-       return !*s;
+       return !*s || *s == '\n';
 }
 
 static inline void strbuf_replace(struct strbuf *sb, const char *a, const char *b)
@@ -91,12 +116,19 @@ static inline void strbuf_replace(struct strbuf *sb, const char *a, const char *
 }
 
 static void free_trailer_item(struct trailer_item *item)
+{
+       free(item->token);
+       free(item->value);
+       free(item);
+}
+
+static void free_arg_item(struct arg_item *item)
 {
        free(item->conf.name);
        free(item->conf.key);
        free(item->conf.command);
-       free((char *)item->token);
-       free((char *)item->value);
+       free(item->token);
+       free(item->value);
        free(item);
 }
 
@@ -111,7 +143,14 @@ static char last_non_space_char(const char *s)
 
 static void print_tok_val(FILE *outfile, const char *tok, const char *val)
 {
-       char c = last_non_space_char(tok);
+       char c;
+
+       if (!tok) {
+               fprintf(outfile, "%s\n", val);
+               return;
+       }
+
+       c = last_non_space_char(tok);
        if (!c)
                return;
        if (strchr(separators, c))
@@ -120,108 +159,70 @@ static void print_tok_val(FILE *outfile, const char *tok, const char *val)
                fprintf(outfile, "%s%c %s\n", tok, separators[0], val);
 }
 
-static void print_all(FILE *outfile, struct trailer_item *first, int trim_empty)
+static void print_all(FILE *outfile, struct list_head *head,
+                     const struct process_trailer_options *opts)
 {
+       struct list_head *pos;
        struct trailer_item *item;
-       for (item = first; item; item = item->next) {
-               if (!trim_empty || strlen(item->value) > 0)
+       list_for_each(pos, head) {
+               item = list_entry(pos, struct trailer_item, list);
+               if ((!opts->trim_empty || strlen(item->value) > 0) &&
+                   (!opts->only_trailers || item->token))
                        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)
+static struct trailer_item *trailer_from_arg(struct arg_item *arg_tok)
 {
-       if (*first)
-               while ((*first)->previous != NULL)
-                       *first = (*first)->previous;
+       struct trailer_item *new = xcalloc(sizeof(*new), 1);
+       new->token = arg_tok->token;
+       new->value = arg_tok->value;
+       arg_tok->token = arg_tok->value = NULL;
+       free_arg_item(arg_tok);
+       return new;
 }
 
 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);
-       }
+                                 struct arg_item *arg_tok)
+{
+       int aoe = after_or_end(arg_tok->conf.where);
+       struct trailer_item *to_add = trailer_from_arg(arg_tok);
+       if (aoe)
+               list_add(&to_add->list, &on_tok->list);
+       else
+               list_add_tail(&to_add->list, &on_tok->list);
 }
 
 static int check_if_different(struct trailer_item *in_tok,
-                             struct trailer_item *arg_tok,
-                             int check_all)
+                             struct arg_item *arg_tok,
+                             int check_all,
+                             struct list_head *head)
 {
-       enum action_where where = arg_tok->conf.where;
+       enum trailer_where where = arg_tok->conf.where;
+       struct list_head *next_head;
        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;
+               next_head = after_or_end(where) ? in_tok->list.prev
+                                               : in_tok->list.next;
+               if (next_head == head)
+                       break;
+               in_tok = list_entry(next_head, struct trailer_item, list);
        } 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)
+static 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;
+       char *result;
 
        strbuf_addstr(&cmd, command);
        if (arg)
@@ -246,7 +247,7 @@ static const char *apply_command(const char *command, const char *arg)
        return result;
 }
 
-static void apply_item_command(struct trailer_item *in_tok, struct trailer_item *arg_tok)
+static void apply_item_command(struct trailer_item *in_tok, struct arg_item *arg_tok)
 {
        if (arg_tok->conf.command) {
                const char *arg;
@@ -264,168 +265,168 @@ static void apply_item_command(struct trailer_item *in_tok, struct trailer_item
 }
 
 static void apply_arg_if_exists(struct trailer_item *in_tok,
-                               struct trailer_item *arg_tok,
+                               struct arg_item *arg_tok,
                                struct trailer_item *on_tok,
-                               struct trailer_item **in_tok_first,
-                               struct trailer_item **in_tok_last)
+                               struct list_head *head)
 {
        switch (arg_tok->conf.if_exists) {
        case EXISTS_DO_NOTHING:
-               free_trailer_item(arg_tok);
+               free_arg_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);
+               add_arg_to_input_list(on_tok, arg_tok);
+               list_del(&in_tok->list);
                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);
+               add_arg_to_input_list(on_tok, arg_tok);
                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);
+               if (check_if_different(in_tok, arg_tok, 1, head))
+                       add_arg_to_input_list(on_tok, arg_tok);
                else
-                       free_trailer_item(arg_tok);
+                       free_arg_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);
+               if (check_if_different(on_tok, arg_tok, 0, head))
+                       add_arg_to_input_list(on_tok, arg_tok);
                else
-                       free_trailer_item(arg_tok);
+                       free_arg_item(arg_tok);
                break;
+       default:
+               die("BUG: trailer.c: unhandled value %d",
+                   arg_tok->conf.if_exists);
        }
 }
 
-static void apply_arg_if_missing(struct trailer_item **in_tok_first,
-                                struct trailer_item **in_tok_last,
-                                struct trailer_item *arg_tok)
+static void apply_arg_if_missing(struct list_head *head,
+                                struct arg_item *arg_tok)
 {
-       struct trailer_item **in_tok;
-       enum action_where where;
+       enum trailer_where where;
+       struct trailer_item *to_add;
 
        switch (arg_tok->conf.if_missing) {
        case MISSING_DO_NOTHING:
-               free_trailer_item(arg_tok);
+               free_arg_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;
-               }
+               to_add = trailer_from_arg(arg_tok);
+               if (after_or_end(where))
+                       list_add_tail(&to_add->list, head);
+               else
+                       list_add(&to_add->list, head);
                break;
+       default:
+               die("BUG: trailer.c: unhandled value %d",
+                   arg_tok->conf.if_missing);
        }
 }
 
-static int find_same_and_apply_arg(struct trailer_item **in_tok_first,
-                                  struct trailer_item **in_tok_last,
-                                  struct trailer_item *arg_tok)
+static int find_same_and_apply_arg(struct list_head *head,
+                                  struct arg_item *arg_tok)
 {
+       struct list_head *pos;
        struct trailer_item *in_tok;
        struct trailer_item *on_tok;
-       struct trailer_item *following_tok;
 
-       enum action_where where = arg_tok->conf.where;
+       enum trailer_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;
+       struct trailer_item *start_tok;
+
+       if (list_empty(head))
+               return 0;
 
-       for (in_tok = start_tok; in_tok; in_tok = following_tok) {
-               following_tok = backwards ? in_tok->previous : in_tok->next;
+       start_tok = list_entry(backwards ? head->prev : head->next,
+                              struct trailer_item,
+                              list);
+
+       list_for_each_dir(pos, head, backwards) {
+               in_tok = list_entry(pos, struct trailer_item, list);
                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);
+               apply_arg_if_exists(in_tok, arg_tok, on_tok, head);
                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)
+static void process_trailers_lists(struct list_head *head,
+                                  struct list_head *arg_head)
 {
-       struct trailer_item *arg_tok;
-       struct trailer_item *next_arg;
-
-       if (!*arg_tok_first)
-               return;
+       struct list_head *pos, *p;
+       struct arg_item *arg_tok;
 
-       for (arg_tok = *arg_tok_first; arg_tok; arg_tok = next_arg) {
+       list_for_each_safe(pos, p, arg_head) {
                int applied = 0;
+               arg_tok = list_entry(pos, struct arg_item, list);
 
-               next_arg = arg_tok->next;
-               remove_from_list(arg_tok, arg_tok_first, NULL);
+               list_del(pos);
 
-               applied = find_same_and_apply_arg(in_tok_first,
-                                                 in_tok_last,
-                                                 arg_tok);
+               applied = find_same_and_apply_arg(head, arg_tok);
 
                if (!applied)
-                       apply_arg_if_missing(in_tok_first,
-                                            in_tok_last,
-                                            arg_tok);
+                       apply_arg_if_missing(head, arg_tok);
        }
 }
 
-static int set_where(struct conf_info *item, const char *value)
+int trailer_set_where(enum trailer_where *item, const char *value)
 {
-       if (!strcasecmp("after", value))
-               item->where = WHERE_AFTER;
+       if (!value)
+               *item = WHERE_DEFAULT;
+       else if (!strcasecmp("after", value))
+               *item = WHERE_AFTER;
        else if (!strcasecmp("before", value))
-               item->where = WHERE_BEFORE;
+               *item = WHERE_BEFORE;
        else if (!strcasecmp("end", value))
-               item->where = WHERE_END;
+               *item = WHERE_END;
        else if (!strcasecmp("start", value))
-               item->where = WHERE_START;
+               *item = WHERE_START;
        else
                return -1;
        return 0;
 }
 
-static int set_if_exists(struct conf_info *item, const char *value)
+int trailer_set_if_exists(enum trailer_if_exists *item, const char *value)
 {
-       if (!strcasecmp("addIfDifferent", value))
-               item->if_exists = EXISTS_ADD_IF_DIFFERENT;
+       if (!value)
+               *item = EXISTS_DEFAULT;
+       else if (!strcasecmp("addIfDifferent", value))
+               *item = EXISTS_ADD_IF_DIFFERENT;
        else if (!strcasecmp("addIfDifferentNeighbor", value))
-               item->if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
+               *item = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
        else if (!strcasecmp("add", value))
-               item->if_exists = EXISTS_ADD;
+               *item = EXISTS_ADD;
        else if (!strcasecmp("replace", value))
-               item->if_exists = EXISTS_REPLACE;
+               *item = EXISTS_REPLACE;
        else if (!strcasecmp("doNothing", value))
-               item->if_exists = EXISTS_DO_NOTHING;
+               *item = EXISTS_DO_NOTHING;
        else
                return -1;
        return 0;
 }
 
-static int set_if_missing(struct conf_info *item, const char *value)
+int trailer_set_if_missing(enum trailer_if_missing *item, const char *value)
 {
-       if (!strcasecmp("doNothing", value))
-               item->if_missing = MISSING_DO_NOTHING;
+       if (!value)
+               *item = MISSING_DEFAULT;
+       else if (!strcasecmp("doNothing", value))
+               *item = MISSING_DO_NOTHING;
        else if (!strcasecmp("add", value))
-               item->if_missing = MISSING_ADD;
+               *item = MISSING_ADD;
        else
                return -1;
        return 0;
 }
 
-static void duplicate_conf(struct conf_info *dst, struct conf_info *src)
+static void duplicate_conf(struct conf_info *dst, const struct conf_info *src)
 {
        *dst = *src;
        dst->name = xstrdup_or_null(src->name);
@@ -433,30 +434,24 @@ static void duplicate_conf(struct conf_info *dst, struct conf_info *src)
        dst->command = xstrdup_or_null(src->command);
 }
 
-static struct trailer_item *get_conf_item(const char *name)
+static struct arg_item *get_conf_item(const char *name)
 {
-       struct trailer_item *item;
-       struct trailer_item *previous;
+       struct list_head *pos;
+       struct arg_item *item;
 
        /* Look up item with same name */
-       for (previous = NULL, item = first_conf_item;
-            item;
-            previous = item, item = item->next) {
+       list_for_each(pos, &conf_head) {
+               item = list_entry(pos, struct arg_item, list);
                if (!strcasecmp(item->conf.name, name))
                        return item;
        }
 
        /* Item does not already exists, create it */
-       item = xcalloc(sizeof(struct trailer_item), 1);
+       item = xcalloc(sizeof(*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;
-       }
+       list_add_tail(&item->list, &conf_head);
 
        return item;
 }
@@ -485,15 +480,18 @@ static int git_trailer_default_config(const char *conf_key, const char *value, v
        variable_name = strrchr(trailer_item, '.');
        if (!variable_name) {
                if (!strcmp(trailer_item, "where")) {
-                       if (set_where(&default_conf_info, value) < 0)
+                       if (trailer_set_where(&default_conf_info.where,
+                                             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)
+                       if (trailer_set_if_exists(&default_conf_info.if_exists,
+                                                 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)
+                       if (trailer_set_if_missing(&default_conf_info.if_missing,
+                                                  value) < 0)
                                warning(_("unknown value '%s' for key '%s'"),
                                        value, conf_key);
                } else if (!strcmp(trailer_item, "separators")) {
@@ -506,7 +504,7 @@ static int git_trailer_default_config(const char *conf_key, const char *value, v
 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 arg_item *item;
        struct conf_info *conf;
        char *name = NULL;
        enum trailer_info_type type;
@@ -547,15 +545,15 @@ static int git_trailer_config(const char *conf_key, const char *value, void *cb)
                conf->command = xstrdup(value);
                break;
        case TRAILER_WHERE:
-               if (set_where(conf, value))
+               if (trailer_set_where(&conf->where, value))
                        warning(_("unknown value '%s' for key '%s'"), value, conf_key);
                break;
        case TRAILER_IF_EXISTS:
-               if (set_if_exists(conf, value))
+               if (trailer_set_if_exists(&conf->if_exists, value))
                        warning(_("unknown value '%s' for key '%s'"), value, conf_key);
                break;
        case TRAILER_IF_MISSING:
-               if (set_if_missing(conf, value))
+               if (trailer_set_if_missing(&conf->if_missing, value))
                        warning(_("unknown value '%s' for key '%s'"), value, conf_key);
                break;
        default:
@@ -564,33 +562,21 @@ static int git_trailer_config(const char *conf_key, const char *value, void *cb)
        return 0;
 }
 
-static int parse_trailer(struct strbuf *tok, struct strbuf *val, const char *trailer)
+static void ensure_configured(void)
 {
-       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;
+       if (configured)
+               return;
+
+       /* Default config must be setup first */
+       default_conf_info.where = WHERE_END;
+       default_conf_info.if_exists = EXISTS_ADD_IF_DIFFERENT_NEIGHBOR;
+       default_conf_info.if_missing = MISSING_ADD;
+       git_config(git_trailer_default_config, NULL);
+       git_config(git_trailer_config, NULL);
+       configured = 1;
 }
 
-static const char *token_from_item(struct trailer_item *item, char *tok)
+static const char *token_from_item(struct arg_item *item, char *tok)
 {
        if (item->conf.key)
                return item->conf.key;
@@ -599,249 +585,417 @@ static const char *token_from_item(struct trailer_item *item, char *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)
+static int token_matches_item(const char *tok, struct arg_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)
+/*
+ * If the given line is of the form
+ * "<token><optional whitespace><separator>..." or "<separator>...", return the
+ * location of the separator. Otherwise, return -1.  The optional whitespace
+ * is allowed there primarily to allow things like "Bug #43" where <token> is
+ * "Bug" and <separator> is "#".
+ *
+ * The separator-starts-line case (in which this function returns 0) is
+ * distinguished from the non-well-formed-line case (in which this function
+ * returns -1) because some callers of this function need such a distinction.
+ */
+static int find_separator(const char *line, const char *separators)
 {
-       struct strbuf tok = STRBUF_INIT;
-       struct strbuf val = STRBUF_INIT;
-       struct trailer_item *item;
-       int tok_len;
+       int whitespace_found = 0;
+       const char *c;
+       for (c = line; *c; c++) {
+               if (strchr(separators, *c))
+                       return c - line;
+               if (!whitespace_found && (isalnum(*c) || *c == '-'))
+                       continue;
+               if (c != line && (*c == ' ' || *c == '\t')) {
+                       whitespace_found = 1;
+                       continue;
+               }
+               break;
+       }
+       return -1;
+}
 
-       if (parse_trailer(&tok, &val, string))
-               return NULL;
+/*
+ * Obtain the token, value, and conf from the given trailer.
+ *
+ * separator_pos must not be 0, since the token cannot be an empty string.
+ *
+ * If separator_pos is -1, interpret the whole trailer as a token.
+ */
+static void parse_trailer(struct strbuf *tok, struct strbuf *val,
+                        const struct conf_info **conf, const char *trailer,
+                        int separator_pos)
+{
+       struct arg_item *item;
+       int tok_len;
+       struct list_head *pos;
 
-       tok_len = token_len_without_separator(tok.buf, tok.len);
+       if (separator_pos != -1) {
+               strbuf_add(tok, trailer, separator_pos);
+               strbuf_trim(tok);
+               strbuf_addstr(val, trailer + separator_pos + 1);
+               strbuf_trim(val);
+       } else {
+               strbuf_addstr(tok, trailer);
+               strbuf_trim(tok);
+       }
 
        /* 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));
+       tok_len = token_len_without_separator(tok->buf, tok->len);
+       if (conf)
+               *conf = &default_conf_info;
+       list_for_each(pos, &conf_head) {
+               item = list_entry(pos, struct arg_item, list);
+               if (token_matches_item(tok->buf, item, tok_len)) {
+                       char *tok_buf = strbuf_detach(tok, NULL);
+                       if (conf)
+                               *conf = &item->conf;
+                       strbuf_addstr(tok, token_from_item(item, tok_buf));
+                       free(tok_buf);
+                       break;
+               }
        }
+}
 
-       return new_trailer_item(NULL,
-                               strbuf_detach(&tok, NULL),
-                               strbuf_detach(&val, NULL));
+static struct trailer_item *add_trailer_item(struct list_head *head, char *tok,
+                                            char *val)
+{
+       struct trailer_item *new = xcalloc(sizeof(*new), 1);
+       new->token = tok;
+       new->value = val;
+       list_add_tail(&new->list, head);
+       return new;
 }
 
-static void add_trailer_item(struct trailer_item **first,
-                            struct trailer_item **last,
-                            struct trailer_item *new)
+static void add_arg_item(struct list_head *arg_head, char *tok, char *val,
+                        const struct conf_info *conf,
+                        const struct new_trailer_item *new_trailer_item)
 {
-       if (!new)
-               return;
-       if (!*last) {
-               *first = new;
-               *last = new;
-       } else {
-               (*last)->next = new;
-               new->previous = *last;
-               *last = new;
+       struct arg_item *new = xcalloc(sizeof(*new), 1);
+       new->token = tok;
+       new->value = val;
+       duplicate_conf(&new->conf, conf);
+       if (new_trailer_item) {
+               if (new_trailer_item->where != WHERE_DEFAULT)
+                       new->conf.where = new_trailer_item->where;
+               if (new_trailer_item->if_exists != EXISTS_DEFAULT)
+                       new->conf.if_exists = new_trailer_item->if_exists;
+               if (new_trailer_item->if_missing != MISSING_DEFAULT)
+                       new->conf.if_missing = new_trailer_item->if_missing;
        }
+       list_add_tail(&new->list, arg_head);
 }
 
-static struct trailer_item *process_command_line_args(struct string_list *trailers)
+static void process_command_line_args(struct list_head *arg_head,
+                                     struct list_head *new_trailer_head)
 {
-       struct trailer_item *arg_tok_first = NULL;
-       struct trailer_item *arg_tok_last = NULL;
-       struct string_list_item *tr;
-       struct trailer_item *item;
+       struct arg_item *item;
+       struct strbuf tok = STRBUF_INIT;
+       struct strbuf val = STRBUF_INIT;
+       const struct conf_info *conf;
+       struct list_head *pos;
 
-       /* 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);
-               }
+       /*
+        * In command-line arguments, '=' is accepted (in addition to the
+        * separators that are defined).
+        */
+       char *cl_separators = xstrfmt("=%s", separators);
+
+       /* Add an arg item for each configured trailer with a command */
+       list_for_each(pos, &conf_head) {
+               item = list_entry(pos, struct arg_item, list);
+               if (item->conf.command)
+                       add_arg_item(arg_head,
+                                    xstrdup(token_from_item(item, NULL)),
+                                    xstrdup(""),
+                                    &item->conf, NULL);
        }
 
-       /* 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);
+       /* Add an arg item for each trailer on the command line */
+       list_for_each(pos, new_trailer_head) {
+               struct new_trailer_item *tr =
+                       list_entry(pos, struct new_trailer_item, list);
+               int separator_pos = find_separator(tr->text, cl_separators);
+
+               if (separator_pos == 0) {
+                       struct strbuf sb = STRBUF_INIT;
+                       strbuf_addstr(&sb, tr->text);
+                       strbuf_trim(&sb);
+                       error(_("empty trailer token in trailer '%.*s'"),
+                             (int) sb.len, sb.buf);
+                       strbuf_release(&sb);
+               } else {
+                       parse_trailer(&tok, &val, &conf, tr->text,
+                                     separator_pos);
+                       add_arg_item(arg_head,
+                                    strbuf_detach(&tok, NULL),
+                                    strbuf_detach(&val, NULL),
+                                    conf, tr);
+               }
        }
 
-       return arg_tok_first;
+       free(cl_separators);
 }
 
-static struct strbuf **read_input_file(const char *file)
+static void read_input_file(struct strbuf *sb, const char *file)
 {
-       struct strbuf **lines;
-       struct strbuf sb = STRBUF_INIT;
-
        if (file) {
-               if (strbuf_read_file(&sb, file, 0) < 0)
+               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)
+               if (strbuf_read(sb, fileno(stdin), 0) < 0)
                        die_errno(_("could not read from stdin"));
        }
+}
 
-       lines = strbuf_split(&sb, '\n');
+static const char *next_line(const char *str)
+{
+       const char *nl = strchrnul(str, '\n');
+       return nl + !!*nl;
+}
 
-       strbuf_release(&sb);
+/*
+ * Return the position of the start of the last line. If len is 0, return -1.
+ */
+static int last_line(const char *buf, size_t len)
+{
+       int i;
+       if (len == 0)
+               return -1;
+       if (len == 1)
+               return 0;
+       /*
+        * Skip the last character (in addition to the null terminator),
+        * because if the last character is a newline, it is considered as part
+        * of the last line anyway.
+        */
+       i = len - 2;
 
-       return lines;
+       for (; i >= 0; i--) {
+               if (buf[i] == '\n')
+                       return i + 1;
+       }
+       return 0;
 }
 
 /*
- * Return the (0 based) index of the start of the patch or the line
- * count if there is no patch in the message.
+ * Return the position of the start of the patch or the length of str if there
+ * is no patch in the message.
  */
-static int find_patch_start(struct strbuf **lines, int count)
+static int find_patch_start(const char *str)
 {
-       int i;
+       const char *s;
 
-       /* Get the start of the patch part if any */
-       for (i = 0; i < count; i++) {
-               if (starts_with(lines[i]->buf, "---"))
-                       return i;
+       for (s = str; *s; s = next_line(s)) {
+               if (starts_with(s, "---"))
+                       return s - str;
        }
 
-       return count;
+       return s - str;
 }
 
 /*
- * 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.
+ * Return the position of the first trailer line or len if there are no
+ * trailers.
  */
-static int find_trailer_start(struct strbuf **lines, int count)
+static int find_trailer_start(const char *buf, size_t len)
 {
-       int start, end_of_title, only_spaces = 1;
+       const char *s;
+       int end_of_title, l, only_spaces = 1;
+       int recognized_prefix = 0, trailer_lines = 0, non_trailer_lines = 0;
+       /*
+        * Number of possible continuation lines encountered. This will be
+        * reset to 0 if we encounter a trailer (since those lines are to be
+        * considered continuations of that trailer), and added to
+        * non_trailer_lines if we encounter a non-trailer (since those lines
+        * are to be considered non-trailers).
+        */
+       int possible_continuation_lines = 0;
 
        /* The first paragraph is the title and cannot be trailers */
-       for (start = 0; start < count; start++) {
-               if (lines[start]->buf[0] == comment_line_char)
+       for (s = buf; s < buf + len; s = next_line(s)) {
+               if (s[0] == comment_line_char)
                        continue;
-               if (contains_only_spaces(lines[start]->buf))
+               if (is_blank_line(s))
                        break;
        }
-       end_of_title = start;
+       end_of_title = s - buf;
 
        /*
-        * Get the start of the trailers by looking starting from the end
-        * for a line with only spaces before lines with one separator.
+        * Get the start of the trailers by looking starting from the end for a
+        * blank line before a set of non-blank lines that (i) are all
+        * trailers, or (ii) contains at least one Git-generated trailer and
+        * consists of at least 25% trailers.
         */
-       for (start = count - 1; start >= end_of_title; start--) {
-               if (lines[start]->buf[0] == comment_line_char)
+       for (l = last_line(buf, len);
+            l >= end_of_title;
+            l = last_line(buf, l)) {
+               const char *bol = buf + l;
+               const char **p;
+               int separator_pos;
+
+               if (bol[0] == comment_line_char) {
+                       non_trailer_lines += possible_continuation_lines;
+                       possible_continuation_lines = 0;
                        continue;
-               if (contains_only_spaces(lines[start]->buf)) {
+               }
+               if (is_blank_line(bol)) {
                        if (only_spaces)
                                continue;
-                       return start + 1;
+                       non_trailer_lines += possible_continuation_lines;
+                       if (recognized_prefix &&
+                           trailer_lines * 3 >= non_trailer_lines)
+                               return next_line(bol) - buf;
+                       else if (trailer_lines && !non_trailer_lines)
+                               return next_line(bol) - buf;
+                       return len;
                }
-               if (strcspn(lines[start]->buf, separators) < lines[start]->len) {
-                       if (only_spaces)
-                               only_spaces = 0;
-                       continue;
+               only_spaces = 0;
+
+               for (p = git_generated_prefixes; *p; p++) {
+                       if (starts_with(bol, *p)) {
+                               trailer_lines++;
+                               possible_continuation_lines = 0;
+                               recognized_prefix = 1;
+                               goto continue_outer_loop;
+                       }
                }
-               return count;
+
+               separator_pos = find_separator(bol, separators);
+               if (separator_pos >= 1 && !isspace(bol[0])) {
+                       struct list_head *pos;
+
+                       trailer_lines++;
+                       possible_continuation_lines = 0;
+                       if (recognized_prefix)
+                               continue;
+                       list_for_each(pos, &conf_head) {
+                               struct arg_item *item;
+                               item = list_entry(pos, struct arg_item, list);
+                               if (token_matches_item(bol, item,
+                                                      separator_pos)) {
+                                       recognized_prefix = 1;
+                                       break;
+                               }
+                       }
+               } else if (isspace(bol[0]))
+                       possible_continuation_lines++;
+               else {
+                       non_trailer_lines++;
+                       non_trailer_lines += possible_continuation_lines;
+                       possible_continuation_lines = 0;
+               }
+continue_outer_loop:
+               ;
        }
 
-       return only_spaces ? count : 0;
+       return len;
 }
 
-/* Get the index of the end of the trailers */
-static int find_trailer_end(struct strbuf **lines, int patch_start)
+/* Return the position of the end of the trailers. */
+static int find_trailer_end(const char *buf, size_t len)
 {
-       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;
+       return len - ignore_non_trailer(buf, len);
 }
 
-static int has_blank_line_before(struct strbuf **lines, int start)
+static int ends_with_blank_line(const char *buf, size_t len)
 {
-       for (;start >= 0; start--) {
-               if (lines[start]->buf[0] == comment_line_char)
-                       continue;
-               return contains_only_spaces(lines[start]->buf);
-       }
-       return 0;
+       int ll = last_line(buf, len);
+       if (ll < 0)
+               return 0;
+       return is_blank_line(buf + ll);
 }
 
-static void print_lines(FILE *outfile, struct strbuf **lines, int start, int end)
+static void unfold_value(struct strbuf *val)
 {
-       int i;
-       for (i = start; lines[i] && i < end; i++)
-               fprintf(outfile, "%s", lines[i]->buf);
+       struct strbuf out = STRBUF_INIT;
+       size_t i;
+
+       strbuf_grow(&out, val->len);
+       i = 0;
+       while (i < val->len) {
+               char c = val->buf[i++];
+               if (c == '\n') {
+                       /* Collapse continuation down to a single space. */
+                       while (i < val->len && isspace(val->buf[i]))
+                               i++;
+                       strbuf_addch(&out, ' ');
+               } else {
+                       strbuf_addch(&out, c);
+               }
+       }
+
+       /* Empty lines may have left us with whitespace cruft at the edges */
+       strbuf_trim(&out);
+
+       /* output goes back to val as if we modified it in-place */
+       strbuf_swap(&out, val);
+       strbuf_release(&out);
 }
 
 static int process_input_file(FILE *outfile,
-                             struct strbuf **lines,
-                             struct trailer_item **in_tok_first,
-                             struct trailer_item **in_tok_last)
+                             const char *str,
+                             struct list_head *head,
+                             const struct process_trailer_options *opts)
 {
-       int count = 0;
-       int patch_start, trailer_start, trailer_end, i;
-
-       /* Get the line count */
-       while (lines[count])
-               count++;
+       struct trailer_info info;
+       struct strbuf tok = STRBUF_INIT;
+       struct strbuf val = STRBUF_INIT;
+       int i;
 
-       patch_start = find_patch_start(lines, count);
-       trailer_end = find_trailer_end(lines, patch_start);
-       trailer_start = find_trailer_start(lines, trailer_end);
+       trailer_info_get(&info, str);
 
        /* Print lines before the trailers as is */
-       print_lines(outfile, lines, 0, trailer_start);
+       if (!opts->only_trailers)
+               fwrite(str, 1, info.trailer_start - str, outfile);
 
-       if (!has_blank_line_before(lines, trailer_start - 1))
+       if (!opts->only_trailers && !info.blank_line_before_trailer)
                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);
+       for (i = 0; i < info.trailer_nr; i++) {
+               int separator_pos;
+               char *trailer = info.trailers[i];
+               if (trailer[0] == comment_line_char)
+                       continue;
+               separator_pos = find_separator(trailer, separators);
+               if (separator_pos >= 1) {
+                       parse_trailer(&tok, &val, NULL, trailer,
+                                     separator_pos);
+                       if (opts->unfold)
+                               unfold_value(&val);
+                       add_trailer_item(head,
+                                        strbuf_detach(&tok, NULL),
+                                        strbuf_detach(&val, NULL));
+               } else if (!opts->only_trailers) {
+                       strbuf_addstr(&val, trailer);
+                       strbuf_strip_suffix(&val, "\n");
+                       add_trailer_item(head,
+                                        NULL,
+                                        strbuf_detach(&val, NULL));
                }
        }
 
-       return trailer_end;
+       trailer_info_release(&info);
+
+       return info.trailer_end - str;
 }
 
-static void free_all(struct trailer_item **first)
+static void free_all(struct list_head *head)
 {
-       while (*first) {
-               struct trailer_item *item = remove_first(first);
-               free_trailer_item(item);
+       struct list_head *pos, *p;
+       list_for_each_safe(pos, p, head) {
+               list_del(pos);
+               free_trailer_item(list_entry(pos, struct trailer_item, list));
        }
 }
 
-static struct tempfile trailers_tempfile;
+static struct tempfile *trailers_tempfile;
 
 static FILE *create_in_place_tempfile(const char *file)
 {
@@ -863,50 +1017,148 @@ static FILE *create_in_place_tempfile(const char *file)
                strbuf_add(&template, file, tail - file + 1);
        strbuf_addstr(&template, "git-interpret-trailers-XXXXXX");
 
-       xmks_tempfile_m(&trailers_tempfile, template.buf, st.st_mode);
+       trailers_tempfile = xmks_tempfile_m(template.buf, st.st_mode);
        strbuf_release(&template);
-       outfile = fdopen_tempfile(&trailers_tempfile, "w");
+       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)
+void process_trailers(const char *file,
+                     const struct process_trailer_options *opts,
+                     struct list_head *new_trailer_head)
 {
-       struct trailer_item *in_tok_first = NULL;
-       struct trailer_item *in_tok_last = NULL;
-       struct trailer_item *arg_tok_first;
-       struct strbuf **lines;
+       LIST_HEAD(head);
+       struct strbuf sb = STRBUF_INIT;
        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);
+       ensure_configured();
 
-       lines = read_input_file(file);
+       read_input_file(&sb, file);
 
-       if (in_place)
+       if (opts->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);
+       trailer_end = process_input_file(outfile, sb.buf, &head, opts);
 
-       process_trailers_lists(&in_tok_first, &in_tok_last, &arg_tok_first);
+       if (!opts->only_input) {
+               LIST_HEAD(arg_head);
+               process_command_line_args(&arg_head, new_trailer_head);
+               process_trailers_lists(&head, &arg_head);
+       }
 
-       print_all(outfile, in_tok_first, trim_empty);
+       print_all(outfile, &head, opts);
 
-       free_all(&in_tok_first);
+       free_all(&head);
 
        /* Print the lines after the trailers as is */
-       print_lines(outfile, lines, trailer_end, INT_MAX);
+       if (!opts->only_trailers)
+               fwrite(sb.buf + trailer_end, 1, sb.len - trailer_end, outfile);
 
-       if (in_place)
+       if (opts->in_place)
                if (rename_tempfile(&trailers_tempfile, file))
                        die_errno(_("could not rename temporary file to %s"), file);
 
-       strbuf_list_free(lines);
+       strbuf_release(&sb);
+}
+
+void trailer_info_get(struct trailer_info *info, const char *str)
+{
+       int patch_start, trailer_end, trailer_start;
+       struct strbuf **trailer_lines, **ptr;
+       char **trailer_strings = NULL;
+       size_t nr = 0, alloc = 0;
+       char **last = NULL;
+
+       ensure_configured();
+
+       patch_start = find_patch_start(str);
+       trailer_end = find_trailer_end(str, patch_start);
+       trailer_start = find_trailer_start(str, trailer_end);
+
+       trailer_lines = strbuf_split_buf(str + trailer_start,
+                                        trailer_end - trailer_start,
+                                        '\n',
+                                        0);
+       for (ptr = trailer_lines; *ptr; ptr++) {
+               if (last && isspace((*ptr)->buf[0])) {
+                       struct strbuf sb = STRBUF_INIT;
+                       strbuf_attach(&sb, *last, strlen(*last), strlen(*last));
+                       strbuf_addbuf(&sb, *ptr);
+                       *last = strbuf_detach(&sb, NULL);
+                       continue;
+               }
+               ALLOC_GROW(trailer_strings, nr + 1, alloc);
+               trailer_strings[nr] = strbuf_detach(*ptr, NULL);
+               last = find_separator(trailer_strings[nr], separators) >= 1
+                       ? &trailer_strings[nr]
+                       : NULL;
+               nr++;
+       }
+       strbuf_list_free(trailer_lines);
+
+       info->blank_line_before_trailer = ends_with_blank_line(str,
+                                                              trailer_start);
+       info->trailer_start = str + trailer_start;
+       info->trailer_end = str + trailer_end;
+       info->trailers = trailer_strings;
+       info->trailer_nr = nr;
+}
+
+void trailer_info_release(struct trailer_info *info)
+{
+       int i;
+       for (i = 0; i < info->trailer_nr; i++)
+               free(info->trailers[i]);
+       free(info->trailers);
+}
+
+static void format_trailer_info(struct strbuf *out,
+                               const struct trailer_info *info,
+                               const struct process_trailer_options *opts)
+{
+       int i;
+
+       /* If we want the whole block untouched, we can take the fast path. */
+       if (!opts->only_trailers && !opts->unfold) {
+               strbuf_add(out, info->trailer_start,
+                          info->trailer_end - info->trailer_start);
+               return;
+       }
+
+       for (i = 0; i < info->trailer_nr; i++) {
+               char *trailer = info->trailers[i];
+               int separator_pos = find_separator(trailer, separators);
+
+               if (separator_pos >= 1) {
+                       struct strbuf tok = STRBUF_INIT;
+                       struct strbuf val = STRBUF_INIT;
+
+                       parse_trailer(&tok, &val, NULL, trailer, separator_pos);
+                       if (opts->unfold)
+                               unfold_value(&val);
+
+                       strbuf_addf(out, "%s: %s\n", tok.buf, val.buf);
+                       strbuf_release(&tok);
+                       strbuf_release(&val);
+
+               } else if (!opts->only_trailers) {
+                       strbuf_addstr(out, trailer);
+               }
+       }
+
+}
+
+void format_trailers_from_commit(struct strbuf *out, const char *msg,
+                                const struct process_trailer_options *opts)
+{
+       struct trailer_info info;
+
+       trailer_info_get(&info, msg);
+       format_trailer_info(out, &info, opts);
+       trailer_info_release(&info);
 }