Re: [PATCH] git-fetch: avoid local fetching from alternate (again)

["Shawn O. Pearce" <spearce@spearce.org>]

Junio C Hamano <gitster@pobox.com> wrote:
> Junio C Hamano <gitster@pobox.com> writes:
> 
> > Well spotted.  It would be a good idea to commit the big comment
> > from contrib/examples/git-fetch.sh to fetch_local_nocopy()
> > function, which would have made us realize that the patch does
> > not refrain from applying this optimization even when shallow
> > is in effect.  But I think that is actually a good change.
> 
> I take this back.  This regresses badly.
> 
> Why?

Whoops.  Good catch.  This is why you had a check for the shallow
history file in git-fetch.sh before you took this optimization path.
My fault for not including it in this patch.
 
> Because the optimization is useless when we are trying to deepen
> the shallow history.  When you are trying to deepen a shallow
> history and the tips of remotes haven't moved since you fetched
> from there the last time, you have everything near the tip, and
> becuse your history is shallow, your ancestry chain is
> cauterized to make it appear that the history is complete.  The
> rev-list reachability test would not fail as we expect.

What about just inserting a check to see if --depth was supplied
to git-fetch on the command line?  If so then we are deepening the
history and we just bypass the rev-list "fast path" test.

I will be posting an updated patch (series now) shortly.

-- 
Shawn.