From: John Keeping <john@keeping.me.uk>
Date: Thu, 24 Oct 2013 21:31:35 GMT
Subject: Re: [PATCH 0/2] finding the fork point from reflog entries
Message-ID: <20131024213134.GD10779@serenity.lan>
In-Reply-To: <xmqqa9hymkma.fsf@gitster.dls.corp.google.com>

On Thu, Oct 24, 2013 at 02:20:29PM -0700, Junio C Hamano wrote:
> John Keeping <john@keeping.me.uk> writes:
> 
> > On Thu, Oct 24, 2013 at 12:11:22PM -0700, Junio C Hamano wrote:
> >> The first one is a clean-up of the code to parse command line
> >> options to "git merge-base".  Options such as "--independent",
> >> "--is-ancestor" and "--octopus" are mutually exclusive and it is
> >> better expressed in terms of the recently introduced OPT_CMDMODE.
> >> 
> >> The second one implements the entire logic of the for loop we see in
> >> "git pull --rebase" directly using get_merge_bases_many() and
> >> postprocessing the result.
> >
> > Nice!  I tried this in the case where the target commit happens to be
> > the 63rd reflog entry:
> >
> > $ time sh -c 'for rev in $(git rev-list -g origin/master 2>/dev/null)
> > do
> >     git merge-base --is-ancestor $rev b2edae0 && break
> > done
> > '
> >
> > real    0m3.772s
> > user    0m3.338s
> > sys     0m0.440s
> >
> > $ time git merge-base --reflog origin/master b2edae0
> >
> > real    0m0.156s
> > user    0m0.138s
> > sys     0m0.018s
> 
> The real question is if the C code computes the same as the shell
> loop.

And in fact it doesn't - if you replace the "break" with "echo $rev" the
shell version prints b2edae0... but the C version prints nothing (and
exists with status 1).