Re: Segfault with merge-tree on multiple Git versions

From: Jeff King <peff@peff.net>
Date: Mar 27, 2013, 20:01 UTC
Message-ID: <20130327200113.GC26380@sigill.intra.peff.net>
In-Reply-To: <20130327194521.GQ2286@serenity.lan>

On Wed, Mar 27, 2013 at 07:45:21PM +0000, John Keeping wrote:

Show 27 quoted lines

> On Wed, Mar 27, 2013 at 02:16:24PM -0500, Jed Brown wrote:
> > Charlie Smurthwaite <charlie@atechmedia.com> writes:
> > 
> > > Yes, I would need to be able to do this on a bare repo for my use case. 
> > 
> > And if it's on the server, you don't want this to be observable, so
> > you don't want HEAD to move around. I don't know a better way than:
> > 
> >   $ git clone --shared -b upstream-branch bare-repo.git /tmp/merge-repo
> >   $ cd /tmp/merge-repo
> >   $ git pull URL incoming-branch
> > 
> > Cloning with --shared just writes a path into .git/objects/info/alternatives
> > and it doesn't need to be on the same file system (unlike --local).
> > 
> > Since 'git merge-tree' just works with trees, it has less information
> > than 'git merge'.
> 
> You could use a temporary index and do something like:
> 
> 	rm -f TMP_INDEX
> 	GIT_INDEX_FILE=TMP_INDEX
> 	export GIT_INDEX_FILE
> 	git read-tree -m $base $ours $theirs &&
> 	git merge-index git-merge-one-file -a
> 
> then inspect that with "git diff-index --cached $ours".

That is precisely how we do it at GitHub. You probably want to add in "--aggressive" to your read-tree to cover a few more simple cases. If there are conflicts, we just bail and say "this can't be merged", and expect the user to do it themselves using git.

-Peff