From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeff King <peff@peff.net>
Subject: Re: Finding a branch point in git
Date: Mon, 28 May 2012 15:06:39 -0400
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To: Felipe Contreras <felipe.contreras@gmail.com>
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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 =C2=A0(master)
> > =C2=A0 =C2=A0 =C2=A0\ =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 /
> > =C2=A0 =C2=A0 =C2=A0 G--H--I---J =C2=A0 (branch X)
> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 \ =C2=A0 =C2=A0/
> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0K--L =C2=A0 =C2=A0(branch =
Y)
> [...]
>=20
> Yes, but then you would need to specify a second branch. I would avoi=
d
> 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".

Maybe you could assume "master", or assume "git symbolic-ref HEAD" as
the second branch?

> There's also another case that doesn't work:
>=20
> -- X -- A -- B (master)
>          \
>           \
>            C (branch A)
>=20
> Shouldn't be hard to add checks for those cases I think.

Actually, I think that one extends naturally. They are never merged, so
your rev-list never finds a merge commit, and you can just take the
merge base of the branch tips.

-Peff