Re: notes handling broken on rebase

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Uwe

On 30/05/2023 10:21, Uwe Kleine-König wrote:
> Hello,
> 
> I found a bug in git rebase and how notes are retained using
> 
> 	uwe@taurus:~/tmp/gittest$ git version
> 	git version 2.41.0.rc2.161.g9c6817b8e7dd
> 
> , it also happens with 2.39.2.
> 
> Here comes a reproducer:

Thanks for reporting this and taking the time to provide an easy 
reproducer. I think the problem is that when git drops the commit in 
do_pick_commit() it still gets recorded as rewritten and so the notes 
are copied. To fix it we need to improve do_pick_commit() to return a 
value indicating that the commit was dropped so that we don't call 
record_in_rewritten() in pick_commits().

Best Wishes

Phillip


>   - Create some initial git history, just three commits A, B and C:
> 
> 	uwe@taurus:~/tmp/gittest$ git init
> 	Initialized empty Git repository in /home/uwe/tmp/gittest/.git/
> 
> 	uwe@taurus:~/tmp/gittest$ for i in A B C; do echo content $i >> file ; git add file ; git commit -m "$i" ; git notes add -m "notes for $i" ; git tag $i ; done
> 	[main (root-commit) db2548de5a3c] A
> 	 1 file changed, 1 insertion(+)
> 	 create mode 100644 file
> 	[main 2b8fa82afb3c] B
> 	 1 file changed, 1 insertion(+)
> 	[main 3dd5e4a2037e] C
> 	 1 file changed, 1 insertion(+)
> 
>   - Pick C on top of A:
> 
> 	uwe@taurus:~/tmp/gittest$ git checkout A
> 	HEAD is now at db2548de5a3c A
> 	uwe@taurus:~/tmp/gittest$ git cherry-pick C
> 	Auto-merging file
> 	CONFLICT (content): Merge conflict in file
> 	error: could not apply 3dd5e4a2037e... C
> 	hint: After resolving the conflicts, mark them with
> 	hint: "git add/rm <pathspec>", then run
> 	hint: "git cherry-pick --continue".
> 	hint: You can instead skip this commit with "git cherry-pick --skip".
> 	hint: To abort and get back to the state before "git cherry-pick",
> 	hint: run "git cherry-pick --abort".
> 	Recorded preimage for 'file'
> 	uwe@taurus:~/tmp/gittest$ { echo content A; echo content C; } > file
> 	uwe@taurus:~/tmp/gittest$ git add file
> 	uwe@taurus:~/tmp/gittest$ git cherry-pick --continue
> 	Recorded resolution for 'file'.
> 	[detached HEAD 6cfc9b7bd437] C
> 	 Date: Tue May 30 11:02:13 2023 +0200
> 	 1 file changed, 1 insertion(+)
> 
>   - Rebase {B, C} on top of A + C' (which results in skipping C):
> 
> 	uwe@taurus:~/tmp/gittest$ git rebase HEAD C
> 	Auto-merging file
> 	CONFLICT (content): Merge conflict in file
> 	error: could not apply 2b8fa82afb3c... B
> 	hint: Resolve all conflicts manually, mark them as resolved with
> 	hint: "git add/rm <conflicted_files>", then run "git rebase --continue".
> 	hint: You can instead skip this commit: run "git rebase --skip".
> 	hint: To abort and get back to the state before "git rebase", run "git rebase --abort".
> 	Recorded preimage for 'file'
> 	Could not apply 2b8fa82afb3c... B
> 	uwe@taurus:~/tmp/gittest$ { echo content A; echo content B; echo content C; } > file
> 	uwe@taurus:~/tmp/gittest$ git add file
> 	uwe@taurus:~/tmp/gittest$ git rebase --continue
> 	Recorded resolution for 'file'.
> 	[detached HEAD e5b3e28216f2] B
> 	 1 file changed, 1 insertion(+)
> 	dropping 3dd5e4a2037ecd31f5470561638cb065434eabbc C -- patch contents already upstream
> 	Successfully rebased and updated detached HEAD.
> 
> Now I have:
> 
> 	uwe@taurus:~/tmp/gittest$ git log --pretty=oneline --abbrev-commit --notes
> 	e5b3e28216f2 (HEAD) B
> 	Notes:
> 	    notes for B
> 	
> 	    notes for C
> 
> 	6cfc9b7bd437 C
> 	db2548de5a3c (tag: A) A
> 	Notes:
> 	    notes for A
> 
> The surprising part here is that (the new) B also has C's note. I would
> have expected that it only has its own one. I quickly looked into the
> source code, but didn't find an easy fix because the code that notices
> that C should be dropped (in do_pick_commit()) isn't where the note is
> copied (which I didn't find).
> 
> Best regards
> Uwe
>