Re: push race

From: Jeff King <peff@peff.net>
Date: Oct 16, 2012, 04:51 UTC
Message-ID: <20121016045118.GA21359@sigill.intra.peff.net>
In-Reply-To: <CAJo=hJu=eqgUhJvvpMLJ05AT6o+nVUDcm+tHV8en8OCX2-2qgA@mail.gmail.com>

On Mon, Oct 15, 2012 at 07:09:52PM -0700, Shawn O. Pearce wrote:

Show 11 quoted lines

> On Mon, Oct 15, 2012 at 11:56 AM, Jeff King <peff@peff.net> wrote:
> > Right. The only thing that needs locking is the refs, because the object
> > database is add-only for normal operations, and by definition collisions
> > mean you have the same content (or are astronomically unlucky, but your
> > consolation prize is that you can write a paper on how you found a sha1
> > collision).
> 
> Its worth nothing that a SHA-1 collision can be identified at the
> server because the server performs a byte-for-byte compare of both
> copies of the object to make sure they match exactly in every way. Its
> not fast, but its safe. :-)

Do we? I thought early versions of git did that, but we did not double-check collisions any more for performance reasons. You don't happen to remember where that code is, do you (not that it really matters, but I am just curious)?

-Peff