Re: Strange merge conflicts against earlier merge.

From: Fredrik Kuivinen <freku045@student.liu.se>
Date: Nov 11, 2005, 07:52 UTC
Message-ID: <20051111075257.GA4765@c165.ib.student.liu.se>
In-Reply-To: <46a038f90511091638k726d605r170717539225a712@mail.gmail.com>

On Thu, Nov 10, 2005 at 01:38:35PM +1300, Martin Langhoff wrote:

Show 42 quoted lines

> We are working with a series of closely related heads, and merging
> among them. I am sometimes finding merge conflicts that I don't think
> I should be seeing. Assuming two branches, 'local' and 'remote', where
> local has with remote before (*), and I have no conflicting changes in
> local...
> 
>  1 - pull and merge from remote. The merge touches file A, B and C
>  2 - on local, develop on unrelated files O,P,Q, commit
>  3 - pull and merge from remote. The merge touches file B, C and D. I
> am sometimes seeing conflicts on file B and C, which was never touched
> on local.
> 
> * - In the case i have, the ancestry before the merge is a bit
> convoluted. AFAIK, this shouldn't affect us going forward. Both
> branches have a common ancestor, though, and are now merging often
> from remote to local.
> 
> We are using cogito for this, although on step 3 I have also tested
> with git-merge.sh and I get the same result.  It could still be a
> problem related to how the merge on step 1 is recording the merge.
> 
> For an example, clone
> http://locke.catalyst.net.nz/git/moodle.git#mdl-artena-tairawhiti and
> register also the
> http://locke.catalyst.net.nz/git/moodle.git#mdl-local branch. Create
> two heads:
> 
>  master: 214e6374d49e6d014f0ba6f159d585a3fe468909
>  remote: 05059be73c9e09e22b98bc796be35c595e551ed6
> 
> On git-merge 'testing merge' master remote you'll see conflicts over
> mod/quiz/editlib.php -- doing the same with cg-merge gets an
> additional conflict on mod/quiz/export.php. Neither of those files
> were ever modified on local -- however, both merges brought in changes
> to the same lines of code.
> 
> I suspect this is because the merge itself is being considered a
> commit on the local branch. Fair enough -- git has no way of ensuring
> that I haven't slipped in a few changes of mine in the merge. OTOH,
> it's pretty unexpected to see this on files that are not one char
> different from the 'remote' branch. Am I doing something wrong?
>

This merge has two common ancestors,

    $ git-merge-base --all master remote
    3b12fc6420c26a6556c2d806fca79dd96e8e22b9
    2163a9076d9515f00494ba9df7dbc85c9804790f

This may explain the results you get with cg-merge, as that script seems to use 'git-merge-base' without the '--all' flag.

It really seems to be the case that there is a real conflict in mod/quiz/editlib.php, this can be visualized nicely with

    gitk master remote -- mod/quiz/editlib.php

- Fredrik