From: Miklos Vajna <vmiklos@frugalware.org>
Date: Fri, 26 Sep 2008 15:15:17 GMT
Subject: Re: [PATCH] builtin-commit: avoid using reduce_heads()
Message-ID: <20080926151517.GV23137@genesis.frugalware.org>
In-Reply-To: <20080926010312.GE6816@neumann>

On Fri, Sep 26, 2008 at 03:03:12AM +0200, SZEDER Gábor <szeder@ira.uka.de> wrote:
> * FAIL 18: Hand committing of a redundant merge removes dups
>         
>         
>                 git rev-parse second master >expect &&
>                 test_must_fail git merge second master &&
>                 git checkout master g &&
>                 EDITOR=: git commit -a &&
>                 git cat-file commit HEAD | sed -n -e "s/^parent //p"
> -e "/^$/q" >actual &&
>                 test_cmp expect actual
>         
>         
> 
> * failed 1 among 18 test(s)
> make: *** [t7502-commit.sh] Error 1

OK, here is the scenario.

The basic problemis that if it's git-commit that creates the merge
commit and not git-merge, then git-commit does not "know" that git-merge
was invoked using --no-ff.

--no-ff means that if reduce_heads() removes a parent, that will be a
problem, since the resulting commit will no longer be a merge commit.

I think we can't avoid storing this info in a MERGE_MODE file, because
we have to add HEAD to the list of parents in case --no-ff is used, but
we should not do so in case it's reachable from existing heads and
--no-ff is not used.

I'll send a patch that does this in a bit.