Subject: Re: [PATCH 8/8] reflog_expire(): lock symbolic refs themselves, not their referent

From: Junio C Hamano <[email-masked]>
Date: Wed, 11 Feb 2015 14:49:46 -0800

Stefan Beller <[email-masked]> writes:

> On Mon, Feb 9, 2015 at 1:12 AM, Michael Haggerty <[email-masked]> wrote:
>> When processing the reflog of a symbolic ref, hold the lock on the
>> symbolic reference itself, not on the reference that it points to.
>
> I am not sure if that makes sense.
> So when expiring HEAD, you want to have a .git/HEAD.lock file
> instead of a .git/refs/heads/master.lock file?
>
> What would happen if there is a concurrent modification
> to the master branch?

The HEAD may be pointing at 'master' and the other party that is
trying to modify it would fail when it tries to update the reflog
for HEAD thanks to HEAD.lock being held by us.  The HEAD may be
pointing at 'next' and the other part that updates 'master' would
not try to modify HEAD reflog and we do not conflict.

At least, I think that is the rationale behind this change.