Re: Re: Updating a submodule with a compatible version from another submodule version using the parent meta-repository

From: Heiko Voigt <hvoigt@hvoigt.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Julian Ibarz <julian.ibarz@gmail.com>,
	Jens Lehmann <Jens.Lehmann@web.de>,
	git@vger.kernel.org
Subject: Re: Re: Updating a submodule with a compatible version from another submodule version using the parent meta-repository
Date: Sat, 29 Jan 2011 12:08:08 +0100	[thread overview]
Message-ID: <20110129110807.GA21864@book.hvoigt.net> (raw)
In-Reply-To: <7v1v3zjp6w.fsf@alter.siamese.dyndns.org>

Hi,

On Wed, Jan 26, 2011 at 02:05:43PM -0800, Junio C Hamano wrote:
> If that version of submodule B is explicitly bound to a commit in the
> superproject A, you know which version of A and C were recorded, and the
> problem is solved.
> 
[...]
> 
> If you are confident that you didn't introduce different kind of
> dependency to other submodules while developing your "old_feature" branch
> in submodule B, one strategy may be to find an ancestor, preferrably the
> fork point, of your "old_feature" branch that is bound to the superproject
> A.  Then at that point at least you know whoever made that commit in A
> tested the combination of what was recorded in that commit, together with
> the version of B and C, and you can go forward from there, replaying the
> changes you made to the "old_feature" branch in submodule B.

Lets extend your explanation a little further and maybe demonstrate the problem
Julian is having a little more. I think what Julian searches for is a tool in
git that does the lookup for you which is AFAIK not that easy currently. It
seems to be a quite useful feature. Here what I understand Julian wants:

1. Find the most recent superproject commit X'' in A that records a submodule
   commit X' in B which contains the commit X in B you are searching for.

   For this we would need use something similar to git describe --contains
   but instead of using the list of existing tags in B it should use the list
   of commits in B which are recorded in A.

   Here a drawing to explain (linear history for simplicity):

   superproject A:

      O---O---X''---O
               \
   submodule B: \
                 \
      O---X---O---X'---O---O

2. Look up the commit of C which is recorded in X'' of A and check it
   out.

Step 2 is easy but for Step 1 the lookup of X' is missing for the commandline.
Is there already anything that implements git describe --contains for a defined
list of commits instead of refs?

Cheers Heiko