Re: [1.8.0] Provide proper remote ref namespaces

[Nicolas Pitre <nico@fluxnic.net>]

On Mon, 7 Feb 2011, Jeff King wrote:

> On Sat, Feb 05, 2011 at 02:55:06PM -0500, Nicolas Pitre wrote:
> 
> > > The latter seems like a regression for the common case of fetching from
> > > two upstreams. E.g., I usually pull from Junio, getting
> > > remotes/origin/v1.7.0.  One day Shawn is the interim maintainer, and I
> > > pull from him, getting remotes/spearce/v1.7.0, which he previously
> > > fetched from Junio. Under the current code, I can still do "git show
> > > v1.7.0"; under the scheme described above I now have to say
> > > "origin/v1.7.0" to disambiguate.
> > 
> > Let's suppose that both tags are identical, as in your scenario above 
> > they would be, then there is no need to call for any ambiguity in that 
> > case.
> 
> Agreed, but...
> 
> > > The real issue, I think, is that we are claiming ambiguity even though
> > > those tags almost certainly point to the same sha1. When handling
> > > ambiguous tags, should we perhaps check to see if all of the ambiguities
> > > point to the same sha1, and in that case, just pick one at random?
> > 
> > If they're identical then there is no randomness.  If they refer to 
> > different tag objects, even if those tag objects do refer to the same 
> > commit object, then I'd say there is an ambiguity only if the tag object 
> > content matters i.e. when displaying the tag content.
> 
> My gut feeling is that they should point to the same tag object, for the
> sake of simplicity (if you are re-tagging a commit under the same name,
> wouldn't I want to know?) and efficiency (we can detect non-ambiguity
> just by looking at the sha1 values without opening objects).

Agreed.  Same tag name referring to same commit but with different tag 
objects is a bit silly and trying to make that case non ambiguous is 
probably going to cause more confusion anyway.  If the tag object is 
different then this is for most purposes a different tag.

> But more importantly, don't we sometimes care where the ref came from?

Not at the moment.  Certainly not with the current flat namespace used 
for tags.

> If I say "git push remote v1.7.4" we do some automagic on the
> destination side of the refspec based on the fact that the source ref
> was found in the refs/tags hierarchy. In the case we're talking about,
> all of the ambiguous refs would presumably also be coming from
> refs/remotes/*/tags/, so they would be functionally equivalent. But I
> wanted to point it out because:
> 
>   1. It is an additional equivalent requirement for two refs to not be
>      ambiguous. They must have the same sha1, _and_ they must have the
>      same "type".

How can this matter?  The same automagic on the destination ref may 
still take place.  Semantically you want to push v1.7.4 so nothing has 
to change there, irrespective of the namespace the v1.7.4 tag comes 
from.  This doesn't matter today, so why would this particular case need 
to change?


Nicolas