Re: [PATCH] Add a 'generation' number to commits

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 16, 2011, 00:36 UTC
Message-ID: <7vvcv3ysc7.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CA+55aFw2_n2NkYpm9c1JiKaX_H4W89Ridq4qzBqyamuxpODejA@mail.gmail.com>

Linus Torvalds <torvalds@linux-foundation.org> writes:

Show 8 quoted lines

> On Fri, Jul 15, 2011 at 12:49 PM, Junio C Hamano <gitster@pobox.com> wrote:
>>
>> I agree this is the way to go if we _were_ to use generation number
>> associated with commit objects in the longer term,
>
> I have to say, if the main issue was "git tag/branch --contains", and
> if the time-based slop approach of the patch I sent out is acceptable,
> I think that we can continue to ignore generation numbers.

I think we are in agreement that "--contains" can be sped up without generation numbers.

As I mentioned elsewhere, rev-list SLOP and merge-base traversal have different performance characteristics and requirements from "--contains" (for one thing, they cannot say "the commit tagged with v2.6.13 is too old that there is no way this commit made three days ago is contained in it" to optimize the traversal). And I agree that if we had generation header in commit in May 2005, optimizing these traversals properly would have been much cleaner, and it may still be worth doing it.