connect: split git:// setup into a separate function
[gitweb.git] / trailer.c
index f0ecde2d2f8b35c565ab176c76882a5fee8d8fb2..3ba157ed0d6157281f0a9e91f7b7f208652adfcc 100644 (file)
--- a/trailer.c
+++ b/trailer.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "config.h"
 #include "string-list.h"
 #include "run-command.h"
 #include "commit.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;
@@ -46,6 +42,8 @@ static LIST_HEAD(conf_head);
 
 static char *separators = ":";
 
+static int configured;
+
 #define TRAILER_ARG_STRING "$ARG"
 
 static const char *git_generated_prefixes[] = {
@@ -60,7 +58,7 @@ static const char *git_generated_prefixes[] = {
                pos != (head); \
                pos = is_reverse ? pos->prev : pos->next)
 
-static int after_or_end(enum action_where where)
+static int after_or_end(enum trailer_where where)
 {
        return (where == WHERE_AFTER) || (where == WHERE_END);
 }
@@ -102,12 +100,12 @@ 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)
@@ -161,13 +159,15 @@ 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 list_head *head, 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;
        list_for_each(pos, head) {
                item = list_entry(pos, struct trailer_item, list);
-               if (!trim_empty || strlen(item->value) > 0)
+               if ((!opts->trim_empty || strlen(item->value) > 0) &&
+                   (!opts->only_trailers || item->token))
                        print_tok_val(outfile, item->token, item->value);
        }
 }
@@ -198,7 +198,7 @@ static int check_if_different(struct trailer_item *in_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 (same_trailer(in_tok, arg_tok))
@@ -297,13 +297,16 @@ static void apply_arg_if_exists(struct trailer_item *in_tok,
                else
                        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 list_head *head,
                                 struct arg_item *arg_tok)
 {
-       enum action_where where;
+       enum trailer_where where;
        struct trailer_item *to_add;
 
        switch (arg_tok->conf.if_missing) {
@@ -318,6 +321,10 @@ static void apply_arg_if_missing(struct list_head *head,
                        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);
        }
 }
 
@@ -328,7 +335,7 @@ static int find_same_and_apply_arg(struct list_head *head,
        struct trailer_item *in_tok;
        struct trailer_item *on_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;
@@ -370,44 +377,50 @@ static void process_trailers_lists(struct list_head *head,
        }
 }
 
-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;
@@ -467,15 +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")) {
@@ -529,15 +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:
@@ -546,6 +562,20 @@ static int git_trailer_config(const char *conf_key, const char *value, void *cb)
        return 0;
 }
 
+static void ensure_configured(void)
+{
+       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 arg_item *item, char *tok)
 {
        if (item->conf.key)
@@ -563,15 +593,32 @@ static int token_matches_item(const char *tok, struct arg_item *item, int tok_le
 }
 
 /*
- * Return the location of the first separator in line, or -1 if there is no
- * separator.
+ * 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)
 {
-       int loc = strcspn(line, separators);
-       if (!line[loc])
-               return -1;
-       return loc;
+       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;
 }
 
 /*
@@ -627,19 +674,27 @@ static struct trailer_item *add_trailer_item(struct list_head *head, char *tok,
 }
 
 static void add_arg_item(struct list_head *arg_head, char *tok, char *val,
-                        const struct conf_info *conf)
+                        const struct conf_info *conf,
+                        const struct new_trailer_item *new_trailer_item)
 {
        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 void process_command_line_args(struct list_head *arg_head,
-                                     struct string_list *trailers)
+                                     struct list_head *new_trailer_head)
 {
-       struct string_list_item *tr;
        struct arg_item *item;
        struct strbuf tok = STRBUF_INIT;
        struct strbuf val = STRBUF_INIT;
@@ -659,77 +714,100 @@ static void process_command_line_args(struct list_head *arg_head,
                        add_arg_item(arg_head,
                                     xstrdup(token_from_item(item, NULL)),
                                     xstrdup(""),
-                                    &item->conf);
+                                    &item->conf, NULL);
        }
 
        /* Add an arg item for each trailer on the command line */
-       for_each_string_list_item(tr, trailers) {
-               int separator_pos = find_separator(tr->string, cl_separators);
+       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->string);
+                       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->string,
+                       parse_trailer(&tok, &val, &conf, tr->text,
                                      separator_pos);
                        add_arg_item(arg_head,
                                     strbuf_detach(&tok, NULL),
                                     strbuf_detach(&val, NULL),
-                                    conf);
+                                    conf, tr);
                }
        }
 
        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
@@ -741,13 +819,13 @@ static int find_trailer_start(struct strbuf **lines, int count)
        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
@@ -755,30 +833,33 @@ static int find_trailer_start(struct strbuf **lines, int count)
         * 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--) {
+       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 (lines[start]->buf[0] == comment_line_char) {
+               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;
                        non_trailer_lines += possible_continuation_lines;
                        if (recognized_prefix &&
                            trailer_lines * 3 >= non_trailer_lines)
-                               return start + 1;
-                       if (trailer_lines && !non_trailer_lines)
-                               return start + 1;
-                       return count;
+                               return next_line(bol) - buf;
+                       else if (trailer_lines && !non_trailer_lines)
+                               return next_line(bol) - buf;
+                       return len;
                }
                only_spaces = 0;
 
                for (p = git_generated_prefixes; *p; p++) {
-                       if (starts_with(lines[start]->buf, *p)) {
+                       if (starts_with(bol, *p)) {
                                trailer_lines++;
                                possible_continuation_lines = 0;
                                recognized_prefix = 1;
@@ -786,8 +867,8 @@ static int find_trailer_start(struct strbuf **lines, int count)
                        }
                }
 
-               separator_pos = find_separator(lines[start]->buf, separators);
-               if (separator_pos >= 1 && !isspace(lines[start]->buf[0])) {
+               separator_pos = find_separator(bol, separators);
+               if (separator_pos >= 1 && !isspace(bol[0])) {
                        struct list_head *pos;
 
                        trailer_lines++;
@@ -797,13 +878,13 @@ static int find_trailer_start(struct strbuf **lines, int count)
                        list_for_each(pos, &conf_head) {
                                struct arg_item *item;
                                item = list_entry(pos, struct arg_item, list);
-                               if (token_matches_item(lines[start]->buf, item,
+                               if (token_matches_item(bol, item,
                                                       separator_pos)) {
                                        recognized_prefix = 1;
                                        break;
                                }
                        }
-               } else if (isspace(lines[start]->buf[0]))
+               } else if (isspace(bol[0]))
                        possible_continuation_lines++;
                else {
                        non_trailer_lines++;
@@ -814,97 +895,95 @@ static int find_trailer_start(struct strbuf **lines, int count)
                ;
        }
 
-       return count;
+       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 list_head *head)
+                             const char *str,
+                             struct list_head *head,
+                             const struct process_trailer_options *opts)
 {
-       int count = 0;
-       int patch_start, trailer_start, trailer_end, i;
+       struct trailer_info info;
        struct strbuf tok = STRBUF_INIT;
        struct strbuf val = STRBUF_INIT;
-       struct trailer_item *last = NULL;
-
-       /* Get the line count */
-       while (lines[count])
-               count++;
+       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++) {
+       for (i = 0; i < info.trailer_nr; i++) {
                int separator_pos;
-               if (lines[i]->buf[0] == comment_line_char)
+               char *trailer = info.trailers[i];
+               if (trailer[0] == comment_line_char)
                        continue;
-               if (last && isspace(lines[i]->buf[0])) {
-                       struct strbuf sb = STRBUF_INIT;
-                       strbuf_addf(&sb, "%s\n%s", last->value, lines[i]->buf);
-                       strbuf_strip_suffix(&sb, "\n");
-                       free(last->value);
-                       last->value = strbuf_detach(&sb, NULL);
-                       continue;
-               }
-               separator_pos = find_separator(lines[i]->buf, separators);
+               separator_pos = find_separator(trailer, separators);
                if (separator_pos >= 1) {
-                       parse_trailer(&tok, &val, NULL, lines[i]->buf,
+                       parse_trailer(&tok, &val, NULL, trailer,
                                      separator_pos);
-                       last = add_trailer_item(head,
-                                               strbuf_detach(&tok, NULL),
-                                               strbuf_detach(&val, NULL));
-               } else {
-                       strbuf_addbuf(&val, lines[i]);
+                       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));
-                       last = NULL;
                }
        }
 
-       return trailer_end;
+       trailer_info_release(&info);
+
+       return info.trailer_end - str;
 }
 
 static void free_all(struct list_head *head)
@@ -916,7 +995,7 @@ static void free_all(struct list_head *head)
        }
 }
 
-static struct tempfile trailers_tempfile;
+static struct tempfile *trailers_tempfile;
 
 static FILE *create_in_place_tempfile(const char *file)
 {
@@ -938,49 +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)
 {
        LIST_HEAD(head);
-       LIST_HEAD(arg_head);
-       struct strbuf **lines;
+       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, &head);
+       trailer_end = process_input_file(outfile, sb.buf, &head, opts);
 
-       process_command_line_args(&arg_head, trailers);
-
-       process_trailers_lists(&head, &arg_head);
+       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, &head, trim_empty);
+       print_all(outfile, &head, opts);
 
        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);
 }