Re: Finding a branch point in git

From: Felipe Contreras <felipe.contreras@gmail.com>
Date: May 31, 2012, 15:27 UTC
Message-ID: <CAMP44s1Q26B9hCdubfDiP2_YUUWGOtyyA=gSwqpGOE4FfZrN8A@mail.gmail.com>
In-Reply-To: <20120530215415.GB3237@sigill.intra.peff.net>

On Wed, May 30, 2012 at 11:54 PM, Jeff King <peff@peff.net> wrote:

Show 31 quoted lines

> On Wed, May 30, 2012 at 07:07:39PM +0200, Felipe Contreras wrote:
>
>> On Mon, May 28, 2012 at 9:06 PM, Jeff King <peff@peff.net> wrote:
>> > On Mon, May 28, 2012 at 02:36:04PM +0200, Felipe Contreras wrote:
>> >
>> >> > What about a history with multiple branches?
>> >> >
>> >> > --X--A--B--C--D----E  (master)
>> >> >      \           /
>> >> >       G--H--I---J   (branch X)
>> >> >           \    /
>> >> >            K--L    (branch Y)
>> >> [...]
>> >>
>> >> Yes, but then you would need to specify a second branch. I would avoid
>> >> that if possible.
>> >
>> > I agree that is less nice. But I don't think the operation is
>> > well-defined with a single branch. If you ask for "when did branch X
>> > split", then in the above graph it is unclear if you meant "split from
>> > master", or "split from Y".
>>
>> If you look from the context that I explained in the first mail; it
>> would be from *any* branch; IOW; find the first commit from branch X
>> (G), and then find the parent. That would be the first commit where
>> branch X started.
>
> I'm not sure that's possible, though, in the face of criss-cross merges.
> How do we distinguish the history above from one in which branch Y was
> forked from master at G, and then branch X was forked from branch Y at
> H?

That is true, but we could use the algorithm used by name-rev: G would have a distance 3 from branch X, and distance 2 from Y, so it would be considered part of branch Y.

Sure, it's not possible to know _for sure_, but this is a bit like renames; we don't really know if a file was renamed or not, but we can make a good guess.

Show 13 quoted lines

>> I think it would be easy to support this case if somehow there was a
>> way to find all the commits that comprise a branch;
>>
>>  % git log branch ^<any-other-branch>
>>
>> I could swear I saw such an option, but I've been looking for days and
>> I can't find it.
>
> I don't think there is such an option. You have to do something like:
>
>  {
>    echo "--not"
>    git for-each-ref --format='%(refname)' | grep -v "^$branch\$"

Rather: git for-each-ref --format='%(refname:short)' refs/heads | grep -v "^$branch\$"

>  } |
>  git rev-list --stdin $branch

Cheers.

-- 
Felipe Contreras