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Re: [PATCH] fix simple deepening of a repo

From
Nicolas Pitre <nico@cam.org>
Date
Aug 24, 2009, 13:55 UTC
Message-ID
<alpine.LFD.2.00.0908240946390.6044@xanadu.home>
In-Reply-To
<7vocq5q0j7.fsf@alter.siamese.dyndns.org>
On Sun, 23 Aug 2009, Junio C Hamano wrote:
Show 35 quoted lines
> Nicolas Pitre <nico@cam.org> writes:
> 
> > If all refs sent by the remote repo during a fetch are reachable 
> > locally, then no further conversation is performed with the remote. This 
> > check is skipped when the --depth argument is provided to allow the 
> > deepening of a shallow clone which corresponding remote repo has no 
> > changed.
> >
> > However, some additional filtering was added in commit c29727d5 to 
> > remove those refs which are equal on both sides.  If the remote repo has 
> > not changed, then the list of refs to give the remote process becomes 
> > empty and simply attempting to deepen a shallow repo always fails.
> >
> > Let's stop being smart in that case and simply send the whole list over
> > when that condition is met.  The remote will do the right thing anyways.
> >
> > Test cases for this issue are also provided.
> >
> > Signed-off-by: Nicolas Pitre <nico@cam.org>
> > ---
> 
> Thanks.  The fix looks correct (as usual with patches from you).
> 
> But it makes me wonder if this logic to filter refs is buying us anything.
> 
> >  	for (rm = refs; rm; rm = rm->next) {
> > +		nr_refs++;
> >  		if (rm->peer_ref &&
> >  		    !hashcmp(rm->peer_ref->old_sha1, rm->old_sha1))
> >  			continue;
> 		ALLOC_GROW(heads, nr_heads + 1, nr_alloc);
> 		heads[nr_heads++] = rm;
> 	}
> 
> What is the point of not asking for the refs that we know are the same?

I could see the advantage if the number of refs is really huge. Wasn't some converted repositories producing a lot of branches and/or tags significantly slowing down a fetch operation? Granted that was long ago when that issue got "fixed" so the details are fuzzy to me.

> In other words, what breaks (not necessarily in the correctness sense, but
> also in the performance sense) if we get rid of this filtering altogether?

If you really want to get rid of that filtering, I'd still do it in a separate patch. That way if any issue appears because of that then bissection will point directly to that removal alone.

Nicolas
Previous: Junio C HamanoNext: Johan Herland
Message 4 of 22 in “git fetch --depth=* broken?”
  1. Nicolas PitreAug 22, 2009
  2. fix simple deepening of a repoNicolas Pitre, Aug 24, 2009
  3. Junio C HamanoAug 24, 2009
  4. Nicolas PitreAug 24, 2009
  5. Johan HerlandAug 24, 2009
  6. Junio C HamanoAug 24, 2009
  7. Daniel BarkalowAug 24, 2009
  8. Julian PhillipsAug 24, 2009
  9. Nicolas PitreAug 25, 2009
  10. Shawn O. PearceAug 25, 2009
  11. Sverre RabbelierAug 25, 2009
  12. Junio C HamanoAug 25, 2009
  13. Shawn O. PearceAug 25, 2009
  14. Junio C HamanoAug 25, 2009
  15. Shawn O. PearceAug 25, 2009
  16. Shawn O. PearceAug 26, 2009
  17. Johannes SixtAug 26, 2009
  18. Shawn O. PearceAug 26, 2009
  19. Junio C HamanoAug 26, 2009
  20. Shawn O. PearceAug 26, 2009
  21. upload-pack: expand capability advertises additional refsShawn O. Pearce, Aug 28, 2009
  22. Junio C HamanoAug 28, 2009

Read the whole thread, see it on lore, or plain text.

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