Merge branch 'jt/use-trailer-api-in-commands'

Commands that operate on a log message and add lines to the trailer
blocks, such as "format-patch -s", "cherry-pick (-x|-s)", and
"commit -s", have been taught to use the logic of and share the
code with "git interpret-trailer".

* jt/use-trailer-api-in-commands:
  sequencer: use trailer's trailer layout
  trailer: have function to describe trailer layout
  trailer: avoid unnecessary splitting on lines
  commit: make ignore_non_trailer take buf/len
  trailer: be stricter in parsing separators

9 files changed, 318 insertions, 198 deletions

diff --git a/builtin/commit.c b/builtin/commit.c
index 8976c3d29b..887ccc7577 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -790,7 +790,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		strbuf_stripspace(&sb, 0);
 
 	if (signoff)
-		append_signoff(&sb, ignore_non_trailer(&sb), 0);
+		append_signoff(&sb, ignore_non_trailer(sb.buf, sb.len), 0);
 
 	if (fwrite(sb.buf, 1, sb.len, s->fp) < sb.len)
 		die_errno(_("could not write commit template"));
diff --git a/commit.c b/commit.c
index 856fd4aeef..2cf85158b4 100644
--- a/commit.c
+++ b/commit.c
@@ -1649,7 +1649,7 @@ const char *find_commit_header(const char *msg, const char *key, size_t *out_len
 }
 
 /*
- * Inspect sb and determine the true "end" of the log message, in
+ * Inspect the given string and determine the true "end" of the log message, in
  * order to find where to put a new Signed-off-by: line.  Ignored are
  * trailing comment lines and blank lines, and also the traditional
  * "Conflicts:" block that is not commented out, so that we can use
@@ -1659,37 +1659,37 @@ const char *find_commit_header(const char *msg, const char *key, size_t *out_len
  * Returns the number of bytes from the tail to ignore, to be fed as
  * the second parameter to append_signoff().
  */
-int ignore_non_trailer(struct strbuf *sb)
+int ignore_non_trailer(const char *buf, size_t len)
 {
 	int boc = 0;
 	int bol = 0;
 	int in_old_conflicts_block = 0;
 
-	while (bol < sb->len) {
-		char *next_line;
+	while (bol < len) {
+		const char *next_line = memchr(buf + bol, '\n', len - bol);
 
-		if (!(next_line = memchr(sb->buf + bol, '\n', sb->len - bol)))
-			next_line = sb->buf + sb->len;
+		if (!next_line)
+			next_line = buf + len;
 		else
 			next_line++;
 
-		if (sb->buf[bol] == comment_line_char || sb->buf[bol] == '\n') {
+		if (buf[bol] == comment_line_char || buf[bol] == '\n') {
 			/* is this the first of the run of comments? */
 			if (!boc)
 				boc = bol;
 			/* otherwise, it is just continuing */
-		} else if (starts_with(sb->buf + bol, "Conflicts:\n")) {
+		} else if (starts_with(buf + bol, "Conflicts:\n")) {
 			in_old_conflicts_block = 1;
 			if (!boc)
 				boc = bol;
-		} else if (in_old_conflicts_block && sb->buf[bol] == '\t') {
+		} else if (in_old_conflicts_block && buf[bol] == '\t') {
 			; /* a pathname in the conflicts block */
 		} else if (boc) {
 			/* the previous was not trailing comment */
 			boc = 0;
 			in_old_conflicts_block = 0;
 		}
-		bol = next_line - sb->buf;
+		bol = next_line - buf;
 	}
-	return boc ? sb->len - boc : 0;
+	return boc ? len - boc : 0;
 }
diff --git a/commit.h b/commit.h
index afd14f318c..9c12abb911 100644
--- a/commit.h
+++ b/commit.h
@@ -355,7 +355,7 @@ extern const char *find_commit_header(const char *msg, const char *key,
 				      size_t *out_len);
 
 /* Find the end of the log message, the right place for a new trailer. */
-extern int ignore_non_trailer(struct strbuf *sb);
+extern int ignore_non_trailer(const char *buf, size_t len);
 
 typedef void (*each_mergetag_fn)(struct commit *commit, struct commit_extra_header *extra,
 				 void *cb_data);
diff --git a/sequencer.c b/sequencer.c
index 30b10ba143..050e28bbc3 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -16,6 +16,7 @@
 #include "refs.h"
 #include "argv-array.h"
 #include "quote.h"
+#include "trailer.h"
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
@@ -56,30 +57,6 @@ static const char *get_todo_path(const struct replay_opts *opts)
 	return git_path_todo_file();
 }
 
-static int is_rfc2822_line(const char *buf, int len)
-{
-	int i;
-
-	for (i = 0; i < len; i++) {
-		int ch = buf[i];
-		if (ch == ':')
-			return 1;
-		if (!isalnum(ch) && ch != '-')
-			break;
-	}
-
-	return 0;
-}
-
-static int is_cherry_picked_from_line(const char *buf, int len)
-{
-	/*
-	 * We only care that it looks roughly like (cherry picked from ...)
-	 */
-	return len > strlen(cherry_picked_prefix) + 1 &&
-		starts_with(buf, cherry_picked_prefix) && buf[len - 1] == ')';
-}
-
 /*
  * Returns 0 for non-conforming footer
  * Returns 1 for conforming footer
@@ -89,49 +66,25 @@ static int is_cherry_picked_from_line(const char *buf, int len)
 static int has_conforming_footer(struct strbuf *sb, struct strbuf *sob,
 	int ignore_footer)
 {
-	char prev;
-	int i, k;
-	int len = sb->len - ignore_footer;
-	const char *buf = sb->buf;
-	int found_sob = 0;
-
-	/* footer must end with newline */
-	if (!len || buf[len - 1] != '\n')
-		return 0;
+	struct trailer_info info;
+	int i;
+	int found_sob = 0, found_sob_last = 0;
 
-	prev = '\0';
-	for (i = len - 1; i > 0; i--) {
-		char ch = buf[i];
-		if (prev == '\n' && ch == '\n') /* paragraph break */
-			break;
-		prev = ch;
-	}
+	trailer_info_get(&info, sb->buf);
 
-	/* require at least one blank line */
-	if (prev != '\n' || buf[i] != '\n')
+	if (info.trailer_start == info.trailer_end)
 		return 0;
 
-	/* advance to start of last paragraph */
-	while (i < len - 1 && buf[i] == '\n')
-		i++;
-
-	for (; i < len; i = k) {
-		int found_rfc2822;
-
-		for (k = i; k < len && buf[k] != '\n'; k++)
-			; /* do nothing */
-		k++;
+	for (i = 0; i < info.trailer_nr; i++)
+		if (sob && !strncmp(info.trailers[i], sob->buf, sob->len)) {
+			found_sob = 1;
+			if (i == info.trailer_nr - 1)
+				found_sob_last = 1;
+		}
 
-		found_rfc2822 = is_rfc2822_line(buf + i, k - i - 1);
-		if (found_rfc2822 && sob &&
-		    !strncmp(buf + i, sob->buf, sob->len))
-			found_sob = k;
+	trailer_info_release(&info);
 
-		if (!(found_rfc2822 ||
-		      is_cherry_picked_from_line(buf + i, k - i - 1)))
-			return 0;
-	}
-	if (found_sob == i)
+	if (found_sob_last)
 		return 3;
 	if (found_sob)
 		return 2;
diff --git a/t/t3511-cherry-pick-x.sh b/t/t3511-cherry-pick-x.sh
index 9cce5ae881..bf0a5c9887 100755
--- a/t/t3511-cherry-pick-x.sh
+++ b/t/t3511-cherry-pick-x.sh
@@ -25,9 +25,8 @@ Signed-off-by: B.U. Thor <buthor@example.com>"
 
 mesg_broken_footer="$mesg_no_footer
 
-The signed-off-by string should begin with the words Signed-off-by followed
-by a colon and space, and then the signers name and email address. e.g.
-Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"
+This is not recognized as a footer because Myfooter is not a recognized token.
+Myfooter: A.U. Thor <author@example.com>"
 
 mesg_with_footer_sob="$mesg_with_footer
 Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"
@@ -112,6 +111,17 @@ test_expect_success 'cherry-pick -s inserts blank line after non-conforming foot
 	test_cmp expect actual
 '
 
+test_expect_success 'cherry-pick -s recognizes trailer config' '
+	pristine_detach initial &&
+	git -c "trailer.Myfooter.ifexists=add" cherry-pick -s mesg-broken-footer &&
+	cat <<-EOF >expect &&
+		$mesg_broken_footer
+		Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>
+	EOF
+	git log -1 --pretty=format:%B >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'cherry-pick -x inserts blank line when conforming footer not found' '
 	pristine_detach initial &&
 	sha1=$(git rev-parse mesg-no-footer^0) &&
diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index ba4902df2b..482112ca33 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -1294,8 +1294,7 @@ EOF
 4:Subject: [PATCH] subject
 8:
 10:Signed-off-by: example happens to be wrapped here.
-11:
-12:Signed-off-by: C O Mitter <committer@example.com>
+11:Signed-off-by: C O Mitter <committer@example.com>
 EOF
 	test_cmp expected actual
 '
@@ -1368,7 +1367,7 @@ EOF
 	test_cmp expected actual
 '
 
-test_expect_success 'signoff: detect garbage in non-conforming footer' '
+test_expect_success 'signoff: tolerate garbage in conforming footer' '
 	append_signoff <<\EOF >actual &&
 subject
 
@@ -1383,8 +1382,36 @@ EOF
 8:
 10:
 13:Signed-off-by: C O Mitter <committer@example.com>
-14:
-15:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'signoff: respect trailer config' '
+	append_signoff <<\EOF >actual &&
+subject
+
+Myfooter: x
+Some Trash
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+11:
+12:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual &&
+
+	test_config trailer.Myfooter.ifexists add &&
+	append_signoff <<\EOF >actual &&
+subject
+
+Myfooter: x
+Some Trash
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+11:Signed-off-by: C O Mitter <committer@example.com>
 EOF
 	test_cmp expected actual
 '
diff --git a/t/t7501-commit.sh b/t/t7501-commit.sh
index d84897a67a..4003a27e6a 100755
--- a/t/t7501-commit.sh
+++ b/t/t7501-commit.sh
@@ -460,6 +460,42 @@ $alt" &&
 	test_cmp expected actual
 '
 
+test_expect_success 'signoff respects trailer config' '
+
+	echo 5 >positive &&
+	git add positive &&
+	git commit -s -m "subject
+
+non-trailer line
+Myfooter: x" &&
+	git cat-file commit HEAD | sed -e "1,/^\$/d" > actual &&
+	(
+		echo subject
+		echo
+		echo non-trailer line
+		echo Myfooter: x
+		echo
+		echo "Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"
+	) >expected &&
+	test_cmp expected actual &&
+
+	echo 6 >positive &&
+	git add positive &&
+	git -c "trailer.Myfooter.ifexists=add" commit -s -m "subject
+
+non-trailer line
+Myfooter: x" &&
+	git cat-file commit HEAD | sed -e "1,/^\$/d" > actual &&
+	(
+		echo subject
+		echo
+		echo non-trailer line
+		echo Myfooter: x
+		echo "Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"
+	) >expected &&
+	test_cmp expected actual
+'
+
 test_expect_success 'multiple -m' '
 
 	>negative &&
diff --git a/trailer.c b/trailer.c
index f0ecde2d2f..11f0b9fb40 100644
--- a/trailer.c
+++ b/trailer.c
@@ -46,6 +46,8 @@ static LIST_HEAD(conf_head);
 
 static char *separators = ":";
 
+static int configured;
+
 #define TRAILER_ARG_STRING "$ARG"
 
 static const char *git_generated_prefixes[] = {
@@ -102,12 +104,12 @@ 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)
@@ -546,6 +548,17 @@ 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 */
+	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 +576,32 @@ 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;
 }
 
 /*
@@ -685,51 +715,71 @@ static void process_command_line_args(struct list_head *arg_head,
 	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 +791,13 @@ 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 +805,33 @@ 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 +839,8 @@ 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 +850,13 @@ 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 +867,64 @@ continue_outer_loop:
 		;
 	}
 
-	return count;
-}
-
-/* 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;
+	return len;
 }
 
-static int has_blank_line_before(struct strbuf **lines, int start)
+/* Return the position of the end of the trailers. */
+static int find_trailer_end(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;
+	return len - ignore_non_trailer(buf, len);
 }
 
-static void print_lines(FILE *outfile, struct strbuf **lines, int start, int end)
+static int ends_with_blank_line(const char *buf, size_t len)
 {
-	int i;
-	for (i = start; lines[i] && i < end; i++)
-		fprintf(outfile, "%s", lines[i]->buf);
+	int ll = last_line(buf, len);
+	if (ll < 0)
+		return 0;
+	return is_blank_line(buf + ll);
 }
 
 static int process_input_file(FILE *outfile,
-			      struct strbuf **lines,
+			      const char *str,
 			      struct list_head *head)
 {
-	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);
+	fwrite(str, 1, info.trailer_start - str, outfile);
 
-	if (!has_blank_line_before(lines, trailer_start - 1))
+	if (!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));
+			add_trailer_item(head,
+					 strbuf_detach(&tok, NULL),
+					 strbuf_detach(&val, NULL));
 		} else {
-			strbuf_addbuf(&val, lines[i]);
+			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)
@@ -951,21 +971,19 @@ void process_trailers(const char *file, int in_place, int trim_empty, struct str
 {
 	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)
 		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);
 
 	process_command_line_args(&arg_head, trailers);
 
@@ -976,11 +994,62 @@ void process_trailers(const char *file, int in_place, int trim_empty, struct str
 	free_all(&head);
 
 	/* Print the lines after the trailers as is */
-	print_lines(outfile, lines, trailer_end, INT_MAX);
+	fwrite(sb.buf + trailer_end, 1, sb.len - trailer_end, outfile);
 
 	if (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);
 }
diff --git a/trailer.h b/trailer.h
index 36b40b8176..65cc5d79c6 100644
--- a/trailer.h
+++ b/trailer.h
@@ -1,7 +1,32 @@
 #ifndef TRAILER_H
 #define TRAILER_H
 
+struct trailer_info {
+	/*
+	 * True if there is a blank line before the location pointed to by
+	 * trailer_start.
+	 */
+	int blank_line_before_trailer;
+
+	/*
+	 * Pointers to the start and end of the trailer block found. If there
+	 * is no trailer block found, these 2 pointers point to the end of the
+	 * input string.
+	 */
+	const char *trailer_start, *trailer_end;
+
+	/*
+	 * Array of trailers found.
+	 */
+	char **trailers;
+	size_t trailer_nr;
+};
+
 void process_trailers(const char *file, int in_place, int trim_empty,
 		      struct string_list *trailers);
 
+void trailer_info_get(struct trailer_info *info, const char *str);
+
+void trailer_info_release(struct trailer_info *info);
+
 #endif /* TRAILER_H */