Re: [BUG] git submodule update is not fail safe

From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Jan 5, 2013, 13:52 UTC
Message-ID: <50E83001.9000505@gmail.com>
In-Reply-To: <7vzk0osjli.fsf@alter.siamese.dyndns.org>

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Il 04/01/2013 22:51, Junio C Hamano ha scritto:

Show 20 quoted lines

> Manlio Perillo <manlio.perillo@gmail.com> writes:
> 
>> $ git submodule update --init
>> ...
>> Submodule 'roms/vgabios' (git://git.qemu.org/vgabios.git/) registered
>> for path 'roms/vgabios'
>> fatal: unable to connect to anongit.freedesktop.org:
>> anongit.freedesktop.org[0: 131.252.210.161]: errno=Connection timed out
>>
>> Unable to fetch in submodule path 'pixman'
>>
>> $ git submodule update --init
>> fatal: Needed a single revision
>> Unable to find current revision in submodule path 'pixman'
>>
>> The problem is easy to solve: manually remove the pixman directory;
>> however IMHO git submodule update should not fail this way since it may
>> confuse the user.
> 
> Sounds like a reasonable observation.  Jens, Heiko, comments?

I have found another, related problem.

Today I tried to update qemu submodules again, however the command failed with an "obscure" error message:

$ git submodule update pixman fatal: Needed a single revision Unable to find current revision in submodule path 'pixman'

The pixman submodule is the one that I failed to update in the very begin. The problem is not with the pixman or qemu repository: if I clone again qemu (with the --recursive option), all is ok.

The problem is with the private working copy (in .git/modules/pixman) being corrupted:

$git log fatal: bad default revision 'HEAD'.

The HEAD file contains "ref: refs/heads/master", but the refs/heads directory is empty.

By the way: since git submodule is a porcelain command, IMHO it should not show to the user these low level error message; at least it should give more details. As an example, in this case it could say something like:

  the local module "pixmap" seems to be corrupted.
  Run xxx to remove the module and yyy to create it again.

The ideal solution is, for submodule update, to never leave an incomplete directory; that is: the update command should be atomic.

Regards  Manlio
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