Re: Finding a branch point in git

From: Jeff King <peff@peff.net>
Date: May 30, 2012, 21:54 UTC
Message-ID: <20120530215415.GB3237@sigill.intra.peff.net>
In-Reply-To: <CAMP44s0UBsVicuEcwACsm1zTT_jGau_Q20hJv4J_6uvancYJRQ@mail.gmail.com>

On Wed, May 30, 2012 at 07:07:39PM +0200, Felipe Contreras wrote:

Show 24 quoted lines

> 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?

Show 7 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\$"
  } |
  git rev-list --stdin $branch

-Peff