Re: [PATCH/RFC] sequencer.c: record revert/cherry-pick commit with trailer lines

[Phillip Wood <phillip.wood@talktalk.net>]

On 04/11/2018 07:22, Nguyễn Thái Ngọc Duy wrote:
> When a commit is reverted (or cherry-picked with -x) we add an English
> sentence recording that commit id in the new commit message. Make
> these real trailer lines instead so that they are more friendly to
> parsers (especially "git interpret-trailers").
> 
> A reverted commit will have a new trailer
> 
>      Revert: <commit-id>
> 
> Similarly a cherry-picked commit with -x will have
> 
>      Cherry-Pick: <commit-id>

I think this is a good idea though I wonder if it will break someones 
script that is looking for the messages generated by -x at the moment. 
I've got a couple of comments below.

> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>   I think standardizing how we record commit ids in the commit message
>   is a good idea. Though to be honest this started because of my irk of
>   an English string "cherry picked from..." that cannot be translated.
>   It might as well be a computer language that happens to look like
>   English.
> 
>   Documentation/git-cherry-pick.txt |  5 ++---
>   sequencer.c                       | 20 ++++++--------------
>   t/t3510-cherry-pick-sequence.sh   | 12 ++++++------
>   t/t3511-cherry-pick-x.sh          | 26 +++++++++++++-------------
>   4 files changed, 27 insertions(+), 36 deletions(-)
> 
> diff --git a/Documentation/git-cherry-pick.txt b/Documentation/git-cherry-pick.txt
> index d35d771fc8..8ffbaed1a0 100644
> --- a/Documentation/git-cherry-pick.txt
> +++ b/Documentation/git-cherry-pick.txt
> @@ -58,9 +58,8 @@ OPTIONS
>   	message prior to committing.
>   
>   -x::
> -	When recording the commit, append a line that says
> -	"(cherry picked from commit ...)" to the original commit
> -	message in order to indicate which commit this change was
> +	When recording the commit, append "Cherry-Pick:" trailer line
> +	recording the commit name which commit this change was
>   	cherry-picked from.  This is done only for cherry
>   	picks without conflicts.  Do not use this option if
>   	you are cherry-picking from your private branch because
> diff --git a/sequencer.c b/sequencer.c
> index 9e1ab3a2a7..f7318f2862 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -36,7 +36,6 @@
>   #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
>   
>   const char sign_off_header[] = "Signed-off-by: ";
> -static const char cherry_picked_prefix[] = "(cherry picked from commit ";
>   
>   GIT_PATH_FUNC(git_path_commit_editmsg, "COMMIT_EDITMSG")
>   
> @@ -1758,16 +1757,10 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
>   		base_label = msg.label;
>   		next = parent;
>   		next_label = msg.parent_label;
> -		strbuf_addstr(&msgbuf, "Revert \"");
> -		strbuf_addstr(&msgbuf, msg.subject);
> -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
> -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> -
> -		if (commit->parents && commit->parents->next) {
> -			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
> -			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
> -		}

As revert currently records the parent given on the command line when 
reverting a merge commit it would probably be a good idea to add that 
either as a separate trailer or to the Revert: trailer and possibly also 
generate it for cherry picks.

> -		strbuf_addstr(&msgbuf, ".\n");
> +		strbuf_addf(&msgbuf, "Revert \"%s\"\n\n", msg.subject);

If the message already contains trailers then should we just append the 
Revert trailer those rather than inserting "\n\n"?

Best Wishes

Phillip

> +
> +		strbuf_addf(&msgbuf, "Revert: %s\n",
> +			    oid_to_hex(&commit->object.oid));

>   	} else {
>   		const char *p;
>   
> @@ -1784,9 +1777,8 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
>   			strbuf_complete_line(&msgbuf);
>   			if (!has_conforming_footer(&msgbuf, NULL, 0))
>   				strbuf_addch(&msgbuf, '\n');
> -			strbuf_addstr(&msgbuf, cherry_picked_prefix);
> -			strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> -			strbuf_addstr(&msgbuf, ")\n");
> +			strbuf_addf(&msgbuf, "Cherry-Pick: %s\n",
> +				    oid_to_hex(&commit->object.oid));
>   		}
>   		if (!is_fixup(command))
>   			author = get_author(msg.message);
> diff --git a/t/t3510-cherry-pick-sequence.sh b/t/t3510-cherry-pick-sequence.sh
> index c84eeefdc9..89b6e7fc1e 100755
> --- a/t/t3510-cherry-pick-sequence.sh
> +++ b/t/t3510-cherry-pick-sequence.sh
> @@ -390,10 +390,10 @@ test_expect_success '--continue respects opts' '
>   	git cat-file commit HEAD~1 >picked_msg &&
>   	git cat-file commit HEAD~2 >unrelatedpick_msg &&
>   	git cat-file commit HEAD~3 >initial_msg &&
> -	! grep "cherry picked from" initial_msg &&
> -	grep "cherry picked from" unrelatedpick_msg &&
> -	grep "cherry picked from" picked_msg &&
> -	grep "cherry picked from" anotherpick_msg
> +	! grep "Cherry-Pick:" initial_msg &&
> +	grep "Cherry-Pick: " unrelatedpick_msg &&
> +	grep "Cherry-Pick: " picked_msg &&
> +	grep "Cherry-Pick: " anotherpick_msg
>   '
>   
>   test_expect_success '--continue of single-pick respects -x' '
> @@ -404,7 +404,7 @@ test_expect_success '--continue of single-pick respects -x' '
>   	git cherry-pick --continue &&
>   	test_path_is_missing .git/sequencer &&
>   	git cat-file commit HEAD >msg &&
> -	grep "cherry picked from" msg
> +	grep "Cherry-Pick:" msg
>   '
>   
>   test_expect_success '--continue respects -x in first commit in multi-pick' '
> @@ -416,7 +416,7 @@ test_expect_success '--continue respects -x in first commit in multi-pick' '
>   	test_path_is_missing .git/sequencer &&
>   	git cat-file commit HEAD^ >msg &&
>   	picked=$(git rev-parse --verify picked) &&
> -	grep "cherry picked from.*$picked" msg
> +	grep "Cherry-Pick: $picked" msg
>   '
>   
>   test_expect_failure '--signoff is automatically propagated to resolved conflict' '
> diff --git a/t/t3511-cherry-pick-x.sh b/t/t3511-cherry-pick-x.sh
> index 9888bf34b9..db11dd2430 100755
> --- a/t/t3511-cherry-pick-x.sh
> +++ b/t/t3511-cherry-pick-x.sh
> @@ -32,7 +32,7 @@ mesg_with_footer_sob="$mesg_with_footer
>   Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"
>   
>   mesg_with_cherry_footer="$mesg_with_footer_sob
> -(cherry picked from commit da39a3ee5e6b4b0d3255bfef95601890afd80709)
> +Cherry-Pick: da39a3ee5e6b4b0d3255bfef95601890afd80709
>   Tested-by: C.U. Thor <cuthor@example.com>"
>   
>   mesg_unclean="$mesg_one_line
> @@ -81,7 +81,7 @@ test_expect_success 'cherry-pick -x inserts blank line after one line subject' '
>   	cat <<-EOF >expect &&
>   		$mesg_one_line
>   
> -		(cherry picked from commit $sha1)
> +		Cherry-Pick: $sha1
>   	EOF
>   	git log -1 --pretty=format:%B >actual &&
>   	test_cmp expect actual
> @@ -129,7 +129,7 @@ test_expect_success 'cherry-pick -x inserts blank line when conforming footer no
>   	cat <<-EOF >expect &&
>   		$mesg_no_footer
>   
> -		(cherry picked from commit $sha1)
> +		Cherry-Pick: $sha1
>   	EOF
>   	git log -1 --pretty=format:%B >actual &&
>   	test_cmp expect actual
> @@ -154,7 +154,7 @@ test_expect_success 'cherry-pick -x -s inserts blank line when conforming footer
>   	cat <<-EOF >expect &&
>   		$mesg_no_footer
>   
> -		(cherry picked from commit $sha1)
> +		Cherry-Pick: $sha1
>   		Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>
>   	EOF
>   	git log -1 --pretty=format:%B >actual &&
> @@ -178,7 +178,7 @@ test_expect_success 'cherry-pick -x -s adds sob when last sob doesnt match commi
>   	git cherry-pick -x -s mesg-with-footer &&
>   	cat <<-EOF >expect &&
>   		$mesg_with_footer
> -		(cherry picked from commit $sha1)
> +		Cherry-Pick: $sha1
>   		Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>
>   	EOF
>   	git log -1 --pretty=format:%B >actual &&
> @@ -201,7 +201,7 @@ test_expect_success 'cherry-pick -x -s adds sob even when trailing sob exists fo
>   	git cherry-pick -x -s mesg-with-footer-sob &&
>   	cat <<-EOF >expect &&
>   		$mesg_with_footer_sob
> -		(cherry picked from commit $sha1)
> +		Cherry-Pick: $sha1
>   		Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>
>   	EOF
>   	git log -1 --pretty=format:%B >actual &&
> @@ -215,7 +215,7 @@ test_expect_success 'cherry-pick -x handles commits with no NL at end of message
>   	git cherry-pick -x $sha1 &&
>   	git log -1 --pretty=format:%B >actual &&
>   
> -	printf "\n(cherry picked from commit %s)\n" $sha1 >>msg &&
> +	printf "\nCherry-Pick: %s\n" $sha1 >>msg &&
>   	test_cmp msg actual
>   '
>   
> @@ -226,7 +226,7 @@ test_expect_success 'cherry-pick -x handles commits with no footer and no NL at
>   	git cherry-pick -x $sha1 &&
>   	git log -1 --pretty=format:%B >actual &&
>   
> -	printf "\n\n(cherry picked from commit %s)\n" $sha1 >>msg &&
> +	printf "\n\nCherry-Pick: %s\n" $sha1 >>msg &&
>   	test_cmp msg actual
>   '
>   
> @@ -252,19 +252,19 @@ test_expect_success 'cherry-pick -s handles commits with no footer and no NL at
>   	test_cmp msg actual
>   '
>   
> -test_expect_success 'cherry-pick -x treats "(cherry picked from..." line as part of footer' '
> +test_expect_success 'cherry-pick -x treats "Cherry-Pick:" line as part of footer' '
>   	pristine_detach initial &&
>   	sha1=$(git rev-parse mesg-with-cherry-footer^0) &&
>   	git cherry-pick -x mesg-with-cherry-footer &&
>   	cat <<-EOF >expect &&
>   		$mesg_with_cherry_footer
> -		(cherry picked from commit $sha1)
> +		Cherry-Pick: $sha1
>   	EOF
>   	git log -1 --pretty=format:%B >actual &&
>   	test_cmp expect actual
>   '
>   
> -test_expect_success 'cherry-pick -s treats "(cherry picked from..." line as part of footer' '
> +test_expect_success 'cherry-pick -s treats "Cherry-Pick:" line as part of footer' '
>   	pristine_detach initial &&
>   	git cherry-pick -s mesg-with-cherry-footer &&
>   	cat <<-EOF >expect &&
> @@ -275,13 +275,13 @@ test_expect_success 'cherry-pick -s treats "(cherry picked from..." line as part
>   	test_cmp expect actual
>   '
>   
> -test_expect_success 'cherry-pick -x -s treats "(cherry picked from..." line as part of footer' '
> +test_expect_success 'cherry-pick -x -s treats "Cherry-Pick:..." line as part of footer' '
>   	pristine_detach initial &&
>   	sha1=$(git rev-parse mesg-with-cherry-footer^0) &&
>   	git cherry-pick -x -s mesg-with-cherry-footer &&
>   	cat <<-EOF >expect &&
>   		$mesg_with_cherry_footer
> -		(cherry picked from commit $sha1)
> +		Cherry-Pick: $sha1
>   		Signed-off-by: $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>
>   	EOF
>   	git log -1 --pretty=format:%B >actual &&
>