From: Thomas Rast <trast@student.ethz.ch>
Date: Sun, 22 Aug 2010 21:58:04 GMT
Subject: Re: git-describe --contains fails on given tree
Message-ID: <201008222358.04504.trast@student.ethz.ch>
In-Reply-To: <alpine.LSU.2.01.1008212241410.23864@obet.zrqbmnf.qr>

Jan Engelhardt wrote:
> 
> On Saturday 2010-08-21 21:55, Jakub Narebski wrote:
> >> for some reason, git-describe cannot figure out v1.17~15^2^2 in
> >> the pam_mount tree, despite me being able to actually give
> >> a description that would fit the contains syntax:
> >What does
> >
> >  $ git describe --contains --tags v1.17~15^2^2
> 
> "Cannot describe 95ce..."
> 
> Funny thing is, describing "v1.17~15^2" does work, as does "v1.17~15^1".

That's clock skew:

  $ git show -s --format="%cd" v1.17~15^2 
  Fri Jan 9 04:35:59 2009 +0100

  $ git show -s --format="%cd" v1.17~15^2^2
  Sat Jan 24 16:35:34 2009 +0100

Note how the parent commit is far newer than the child.  git-name-rev
(which is what really drives git describe --contains) concludes that
it can stop searching along this line of history.

Interestingly, --stdin disables this optimization:

  $ git rev-parse v1.17~15^2^2 | git name-rev --stdin
  95ce932690dfce8cbe50b6a3a8949e41a54c8966 (tags/v1.17~15^2^2)

-- 
Thomas Rast
trast@{inf,student}.ethz.ch