Re: [PATCH] add receive.denyNonFastforwards config variable

[Junio C Hamano <junkio@cox.net>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> On Wed, 20 Sep 2006, Junio C Hamano wrote:
>
>> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>> 
>> > 	No longer barfs on new refs, and tries all merge bases (even if I
>> > 	cannot come up with any scenario where there is more than one merge
>> > 	base in the case of a fast forward).
>> 
>> Hmm.  If that is the case (and I think it is although I haven't
>> come up with a proof),
>
> From git-fetch.sh:
>
>             # Require fast-forward.
>             mb=$(git-merge-base "$local" "$2") &&
>...
> So we indeed assumed that git-merge-base returns the old commit in the 
> case of a fast-forward (git-merge-base returns just the first item of the 
> result of get_merge_bases()).

I think this was leftover from the days we naïvely assumed that
multiple bases does not matter, and probably needs updating.

> Note that I have no proof that this assumption is true. It might be wrong 
> in this case:
>
>     X - a - b - c - Y
>   /           /
> o - d - e - f
>
> where X is the old commit, and Y is the new commit. But I am too tired to 
> test it right now.