From: Geert Uytterhoeven <geert.uytterhoeven@sonycom.com>
Date: Fri, 20 Feb 2009 14:31:22 GMT
Subject: Re: Recovering from missing objects?
Message-ID: <alpine.LRH.2.00.0902201440140.18017@vixen.sonytel.be>
In-Reply-To: <7vvdr6j6hz.fsf@gitster.siamese.dyndns.org>

	Hi Junio,

On Thu, 19 Feb 2009, Junio C Hamano wrote:
> Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com> writes:
> > I start to see suspicious messages about missing objects in one of my working
> > repositories:
> >
> > | vixen$ git gc
> > | error: Could not read c406ab0be69c912ea59233595a071478103cdad8
> > | fatal: bad tree object c406ab0be69c912ea59233595a071478103cdad8
> > | error: failed to run repack
> > | vixen$ 
> >
> > I identified the missing object listed above to be part of a remote repository.
> > Doing a `git remote update' doesn't fetch it again, as git is too smart and
> > thinks I already have everything.
> >
> > If I clone the remote repository, I have the object in the new clone.
> > However, how do I get the missing object back into the .git directory of my
> > working repository?
> 
> In the new clone:
> 
> 	$ IT=c406ab0be69c912ea59233595a071478103cdad8
> 	$ TYPE=$(git cat-file -t $IT)
>         $ git cat-file $TYPE $IT >/var/tmp/$IT.raw
> 
> Go to the repository that lacks the object and then
> 
> 	$ git hash-object -t $TYPE -w --stdin </var/tmp/$IT.raw
> 
> After that you may find objects that $IT needs to reference.  You can
> obviously repeat the above procedure until you have nothing missing.

Thanks! It worked fine for most of the missing objects.

For some of them (type commit), I still get:

| vixen$ git show 32582324956483840d1ae90726bbe879cc48f63d
| fatal: unable to read destination tree (32582324956483840d1ae90726bbe879cc48f63d
| vixen$ 

after importing it from the other repository.

> I also suspect you could do this instead; I haven't thought things through
> and that is why I say "suspect" but this is safe (i.e. not destructive)
> and may worth a try.
> 
> In the new clone:
> 
> 	$ IT=c406ab0be69c912ea59233595a071478103cdad8
> 	$ H=$(git rev-list --objects $IT | git pack-objects mine)
>         $ mv mine-$H.pack /var/tmp
> 
> Go to the repository that lacks the object and then
> 
> 	$ git unpack-objects </var/tmp/mine-$H.pack

That one did the trick for the "stubborn" commits I couldn't get imported the
other way.

BTW, I kept a copy of the repository with the missing commit
32582324956483840d1ae90726bbe879cc48f63d, just in case you have another idea to
revive that single one without creating a (big) pack ;-)

Anyway, I think it wouldn't hurt to have an option for "git remote update" to
retrieve all lost commits from the remote...

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre Europe
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

Phone:    +32 (0)2 700 8453
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E-mail:   Geert.Uytterhoeven@sonycom.com
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