From: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Date: Wed, 14 Oct 2015 14:38:37 GMT
Subject: Re: repository corruption when pushing commits to a repository running 'git gc --prune='
Message-ID: <vpq4mhtbjma.fsf@grenoble-inp.fr>
In-Reply-To: <561E5C5B.3090207@alcatel-lucent.com>

Jan Smets <jan.smets@alcatel-lucent.com> writes:

> Hi
>
> I've recently expired my reflog to prune loose objects. On a live,
> bare, repository I ran 'git gc --prune=now'
>
> All clients ended up having problems, they would report:
>  error: refs/heads/master does not point to a valid object!
> Running 'git log' on the bare repo gave : fatal: bad object HEAD
[...]
> fatal: bad object 22f0351258fa0bb4cd28984b6473510957fbce69
> fatal: bad object 22f0351258fa0bb4cd28984b6473510957fbce69
> To /tmp/test/bare
>  ! [remote rejected] master -> master (missing necessary objects)

I think this is the expected behavior. push will create new objects that
are not referenced until the ref is updated (at the very end). prune can
run concurrently since creating and deleting objects is done in a
lockless way (only the ref update needs a lock).

Still, this is not the *documented* behavior, and an easy way to corrupt
a repo should be very explicitly documented as very dangerous, and the
precautions to take when using it should be explained clearly.

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/