From e69bbfa2947ee733a2b76f1dc28ceaf415368f2a Mon Sep 17 00:00:00 2001 From: Ayush Chandekar Date: Wed, 16 Jul 2025 17:13:28 +0530 Subject: commit: avoid scanning trailing comments when 'core.commentChar' is "auto" When core.commentChar is set to "auto", Git selects a comment character by scanning the commit message contents and avoiding any character already present in the message. If the message still contains old conflict comments (starting with a comment character), Git assumes that character is in use and chooses a different one. As a result, those existing comment lines are no longer recognized as comments and end up being included in the final commit message. To avoid this, skip scanning the trailing comment block when selecting the comment character. This allows Git to safely reuse the original character when appropriate, keeping the commit message clean and free of leftover conflict information. Background: The "auto" value for core.commentchar was introduced in the commit 84c9dc2c5a (commit: allow core.commentChar=auto for character auto selection, 2014-05-17) but did not exhibit this issue at that time. The bug was introduced in commit a6c2654f83 (rebase -m: fix --signoff with conflicts, 2024-04-18) where Git started writing conflict comments to the file at 'rebase_path_message()'. Mentored-by: Christian Couder Mentored-by: Ghanshyam Thakkar Signed-off-by: Ayush Chandekar Signed-off-by: Junio C Hamano --- builtin/commit.c | 6 +++++- t/t3418-rebase-continue.sh | 13 +++++++++++++ 2 files changed, 18 insertions(+), 1 deletion(-) 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/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 && -- cgit 1.2.3-korg From 92b7c7c9f5fde4972a653ddb90eca52c592de07e Mon Sep 17 00:00:00 2001 From: Ayush Chandekar Date: Wed, 16 Jul 2025 17:13:29 +0530 Subject: config: set comment_line_str to "#" when core.commentChar=auto If conflict comments already use a comment character that isn't "#", and core.commentChar is set "auto", Git will ignore these lines during the scan using ignored_log_message_bytes() and pick a new comment character based on the rest of the message. The newly chosen character may be different from the one used in the conflict comments and therefore, these are no longer treated as comments and end up in the final commit message. For example, during a rebase if the user previously set core.commentChar=% and then encounters a conflict, conflict comments like "% Conflicts:" are generated. If the user subsequently sets core.commentChar=auto before running `rebase --continue`, Git parses the "auto" setting and begins scanning. It first uses the existing 'comment_line_str' (which is '%') to detect and ignore conflict comments via ignored_log_message_bytes(). Then, Git scans the rest of the message (excluding conflict comments), sees that none of the remaining lines start with '#' and decides to set comment_line_str to '#'. Since the final commit character differs from the one used in the conflict comments, those lines are no longer considered comments and get included in the final commit message. Set 'comment_line_str' to '#' when core.commentChar is set to 'auto' to reset any previously set value. While this does not solve the issue of conflict comment inclusion and the user visible behaviour stays tha same, it standardizes the behaviour of the code by always resetting 'comment_line_str' to '#' when core.commentChar=auto is parsed. The patch text is based on Phillip Wood's message: https://lore.kernel.org/git/9e96aaab-79a2-4632-94cd-d016d4a63b30@gmail.com/ and the commit log message is wriiten by me. Signed-off-by: Phillip Wood Mentored-by: Christian Couder Mentored-by: Ghanshyam Thakkar Signed-off-by: Ayush Chandekar Signed-off-by: Junio C Hamano --- config.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/config.c b/config.c index b18b5617fc..98548578a3 100644 --- a/config.c +++ b/config.c @@ -1537,9 +1537,11 @@ 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; -- cgit 1.2.3-korg