Re: Git commit generation numbers

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Jul 14, 2011, 19:23 UTC
Message-ID: <CA+55aFx=ACnVBGU8_9wa=9xTbxVoOWKnsqfmBvzq7qzOeMGSNA@mail.gmail.com>
In-Reply-To: <20110714190844.GA26918@sigill.intra.peff.net>

On Thu, Jul 14, 2011 at 12:08 PM, Jeff King <peff@peff.net> wrote:

>
> If we aren't going to go whole-hog on generation numbers, I'm much more
> tempted to simply keep using commit timestamps.

Sure. I think it's entirely reasonable to say that the issue basically boils down to one git question: "can commit X be an ancestor of commit Y" (as a way to basically limit certain algorithms from having to walk all the way down). We've used commit dates for it, and realistically it really has worked very well. But it was always a broken heuristic.

So yes, I personally see generation counters as a way to do the commit date comparisons right. And it would be perfectly fine to just say "if there are no generation numbers, we'll use the datestamps instead, and know that they could be incorrect".

That "use the datestamps" fallback thing may well involve all the heuristics we already do (ie check for the stamps looking sane, and not trusting just one individual one).

                           Linus