From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 14 Jul 2011 18:55:39 GMT
Subject: Re: Git commit generation numbers
Message-ID: <CA+55aFzvib7QF-J3fBj2brcQifXGqoeK1t7vfx6pcJmJAEO0dw@mail.gmail.com>
In-Reply-To: <CA+55aFwuK+krTA4OcnYhLXtKM5HQ1yuPK+J_vC-5R7AthrHWbg@mail.gmail.com>

On Thu, Jul 14, 2011 at 11:47 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Also, I suspect that the cache could easily be done as a *small* and
> *incomplete* cache, ie you don't need to cache all commits, it would
> be sufficient to cache a few hundred spread-out commits, and just know
> that "from any commit, the cached commit will be quickly reachable".

Put another way: we could do the cache not as a real dynamic entity,
but as something that gets generated at "git clone" time or when
re-packing.

I'm actually much more nervous about a cache being inconsistent than I
would be about having generation numbers in the tree. The latter we
can (and should - but my patch didn't) add a fsck test for, and then
you would never get into some situation where there's some really
subtle issue with merge base calculation due to a corrupt cache.

                    Linus