Re: [PATCH] rebase -r: always reword merge -c

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Phillip,

On Fri, 26 Apr 2019, Phillip Wood wrote:

> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>
> If a merge can be fast-forwarded then make sure that we still edit the
> commit message if the user specifies -c. The implementation follows the
> same pattern that is used for ordinary rewords that are fast-forwarded.
>
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> ---

OMG I was bitten twice by this very bug in the past week, and planned on
looking into it next week. Thanks for beating me to it.

Two comments:

> diff --git a/sequencer.c b/sequencer.c
> index 0db410d590..ff8565e7a8 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -3248,6 +3248,10 @@ static int do_merge(struct repository *r,
>  		rollback_lock_file(&lock);
>  		ret = fast_forward_to(r, &commit->object.oid,
>  				      &head_commit->object.oid, 0, opts);
> +		if (flags & TODO_EDIT_MERGE_MSG) {
> +			run_commit_flags |= AMEND_MSG;
> +			goto fast_forward_edit;
> +		}
>  		goto leave_merge;
>  	}
>
> @@ -3351,6 +3355,7 @@ static int do_merge(struct repository *r,
>  		 * value (a negative one would indicate that the `merge`
>  		 * command needs to be rescheduled).
>  		 */
> +	fast_forward_edit:

It is *slightly* awkward that this is an `else` arm of an `if (ret)`, but
I do not necessarily think that it would be better to move the label
before the `if` than what you did; Your version comes out more readable,
still.

>  		ret = !!run_git_commit(r, git_path_merge_msg(r), opts,
>  				       run_commit_flags);
>
> diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
> index 4c69255ee6..3d484a3c72 100755
> --- a/t/t3430-rebase-merges.sh
> +++ b/t/t3430-rebase-merges.sh
> @@ -164,6 +164,16 @@ test_expect_success 'failed `merge <branch>` does not crash' '
>  	grep "^Merge branch ${SQ}G${SQ}$" .git/rebase-merge/message
>  '
>
> +test_expect_success 'fast-forward merge -c still rewords' '
> +	git checkout -b fast-forward-merge-c H &&
> +	set_fake_editor &&

set_fake_editor affects global state AFAIR (setting and exporting
`EDITOR`), therefore this would need to be run in a subshell, i.e.
enclosed in parentheses.

> +	FAKE_COMMIT_MESSAGE=edited GIT_SEQUENCE_EDITOR="echo merge -c H G >" \
> +		git rebase -ir @^ &&
> +	echo edited >expected &&
> +	git log --pretty=format:%B -1 >actual &&
> +	test_cmp expected actual
> +'
> +

The rest looks good, thank you!
Dscho

>  test_expect_success 'with a branch tip that was cherry-picked already' '
>  	git checkout -b already-upstream master &&
>  	base="$(git rev-parse --verify HEAD)" &&
> --
> 2.21.0
>
>