Re: [RFC PATCH] GIT-VERSION-GEN: set --abbrev=9 to match auto-scaling

From: Jeff King <peff@peff.net>
Date: Dec 6, 2016, 14:03 UTC
Message-ID: <20161206140259.lly76xkvsj7su3om@sigill.intra.peff.net>
In-Reply-To: <xmqqbmwq5k7k.fsf@gitster.mtv.corp.google.com>

On Mon, Dec 05, 2016 at 10:01:19AM -0800, Junio C Hamano wrote:

Show 15 quoted lines

> > That said, I think the right patch may be to just drop --abbrev
> > entirely.
> > ...
> > I think at that point it was a noop, as 7 should have been the default.
> > And now we probably ought to drop it, so that we can use the
> > auto-scaling default.
> 
> Yeah, I agree.
> 
> It does mean that snapshot binaries built out of the same commit in
> the same repository before and after a repack have higher chances of
> getting named differently, which may surprise people, but that
> already is possible with a fixed length if the repacking involves
> pruning (albeit with lower probabilities), and I do not think it is
> a problem.

I think that the number is already unstable, even with --abbrev, as it just specifies a minimum. So any operation that creates objects has a possibility of increasing the length. Or more likely, two people describing the same version may end up with different strings because they have different objects in their repositories (e.g., I used to carry's trast's git-notes archive of the mailing list which added quite a few objects).

I agree that having it change over the course of a repack is slightly _more_ surprising than those cases, but ultimately the value just isn't stable.

-Peff