Merge branch 'ac/auto-comment-char-fix'

"git commit" that concludes a conflicted merge failed to notice and remove
existing comment added automatically (like "# Conflicts:") when the
core.commentstring is set to 'auto'.

* ac/auto-comment-char-fix:
  config: set comment_line_str to "#" when core.commentChar=auto
  commit: avoid scanning trailing comments when 'core.commentChar' is "auto"

3 files changed, 22 insertions, 3 deletions

diff --git a/builtin/commit.c b/builtin/commit.c
index fba0dded64..63e7158e98 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -688,6 +688,10 @@ static void adjust_comment_line_char(const struct strbuf *sb)
 	char candidates[] = "#;@!$%^&|:";
 	char *candidate;
 	const char *p;
+	size_t cutoff;
+
+	/* Ignore comment chars in trailing comments (e.g., Conflicts:) */
+	cutoff = sb->len - ignored_log_message_bytes(sb->buf, sb->len);
 
 	if (!memchr(sb->buf, candidates[0], sb->len)) {
 		free(comment_line_str_to_free);
@@ -700,7 +704,7 @@ static void adjust_comment_line_char(const struct strbuf *sb)
 	candidate = strchr(candidates, *p);
 	if (candidate)
 		*candidate = ' ';
-	for (p = sb->buf; *p; p++) {
+	for (p = sb->buf; p + 1 < sb->buf + cutoff; p++) {
 		if ((p[0] == '\n' || p[0] == '\r') && p[1]) {
 			candidate = strchr(candidates, p[1]);
 			if (candidate)
diff --git a/config.c b/config.c
index c90b544231..8a2d0b7916 100644
--- a/config.c
+++ b/config.c
@@ -1534,9 +1534,11 @@ static int git_default_core_config(const char *var, const char *value,
 	    !strcmp(var, "core.commentstring")) {
 		if (!value)
 			return config_error_nonbool(var);
-		else if (!strcasecmp(value, "auto"))
+		else if (!strcasecmp(value, "auto")) {
 			auto_comment_line_char = 1;
-		else if (value[0]) {
+			FREE_AND_NULL(comment_line_str_to_free);
+			comment_line_str = "#";
+		} else if (value[0]) {
 			if (strchr(value, '\n'))
 				return error(_("%s cannot contain newline"), var);
 			comment_line_str = value;
diff --git a/t/t3418-rebase-continue.sh b/t/t3418-rebase-continue.sh
index 127216f722..b8a8dd77e7 100755
--- a/t/t3418-rebase-continue.sh
+++ b/t/t3418-rebase-continue.sh
@@ -328,6 +328,19 @@ test_expect_success 'there is no --no-reschedule-failed-exec in an ongoing rebas
 	test_expect_code 129 git rebase --edit-todo --no-reschedule-failed-exec
 '
 
+test_expect_success 'no change in comment character due to conflicts markers with core.commentChar=auto' '
+	git checkout -b branch-a &&
+	test_commit A F1 &&
+	git checkout -b branch-b HEAD^ &&
+	test_commit B F1 &&
+	test_must_fail git rebase branch-a &&
+	printf "B\nA\n" >F1 &&
+	git add F1 &&
+	GIT_EDITOR="cat >actual" git -c core.commentChar=auto rebase --continue &&
+	# Check that "#" is still the comment character.
+	test_grep "^# Changes to be committed" actual
+'
+
 test_orig_head_helper () {
 	test_when_finished 'git rebase --abort &&
 		git checkout topic &&