Re: [1.8.0] Provide proper remote ref namespaces

["Santi Béjar" <santi@agolina.net>]

On Wed, Feb 2, 2011 at 4:51 PM, Johan Herland <johan@herland.net> wrote:
> On Wednesday 02 February 2011, Santi Béjar wrote:
>> On Wednesday 02 February 2011, Johan Herland wrote:
>> > Proposal:
>> >
>> > Currently, git stores remote refs in the local repo by default as
>> > follows:
>> >
>> >  Remote repo    ->   Local repo
>> >  ---------------------------------------------------------
>> >  HEAD                refs/remotes/$remote/HEAD  (implicit)
>> >  refs/heads/*        refs/remotes/$remote/*
>> >  refs/tags/*         refs/tags/*         (implicit, autofollow)
>> >  refs/replace/*      (TBD)
>> >  refs/notes/*        (TBD)
>> >
>> > Instead, we should change the default ref mappings into the
>> > following:
>> >
>> >  Remote repo    ->   Local repo
>> >  --------------------------------------------------
>> >  HEAD                refs/remotes/$remote/HEAD
>> >  refs/heads/*        refs/remotes/$remote/heads/*
>> >  refs/tags/*         refs/remotes/$remote/tags/*
>> >  refs/replace/*      refs/remotes/$remote/replace/*
>> >  refs/notes/*        refs/remotes/$remote/notes/*
>>
>> [...]
>>
>> > - We might want to generalize the handling of "$remote/$head" into
>> > allowing shorthands like "$remote/$tag", "$remote/$replace" and
>> > "$remote/$note" as well (provided, of course, that they match
>> > unambiguously).
>>
>> [...]
>>
>> > [2]: When looking up a shorthand tag name (e.g. v1.7.4): If a local
>> > tag (refs/tags/v1.7.4) is found, then we have an unambiguous match.
>> > If no local tag is found, we look up the tag name in all configured
>> > remotes (using the method described in [1]). If the tag name exists
>> > in one or more remotes, and those remotes all agree on its ultimate
>> > object name (after applying e.g. ^{commit} or whatever is
>> > appropriate in the context of the lookup), then we also have an
>> > unambiguous match. However, if the tag name exists in multiple
>> > remotes, and they do NOT all agree on its ultimate object name,
>> > then the shorthand tag name is ambiguous and the lookup fails. The
>> > user can always resolve this ambiguity by creating a local tag
>> > (refs/tags/v1.7.4) pointing to the desired object.
>>
>> And the other way around. What would be the output of "git name-rev"
>> , "git describe", "--decorate", and such? $remote/tags/$tag?
>> $remote/$tag? $tag?
>>
>> I would say $remote/$tag for "git name-rev" and "--decorate" but $tag
>> for "git describe" as it is usually used to create files, i.e.
>> git-1.7.4.261.g705f.tar.gz. And I think many people, me included, do
>> not expect to have an / in the "git describe" output, at least in the
>> default output (in contrast with the --all flag).
>
> Thanks for raising an important point.
>
> I don't buy the file name creation argument, as 'describe' is used from
> many different contexts, and file name creation is nowhere documented
> as one of its primary objectives.

Yes, I know it is used from many different contexts, but one important
one is the creation of the tar files, even git.git's Makefile assumes
this. But as at the end we agree...

>
> Still, the objective of 'describe' is to create a human-readable string
> that tries to say something meaningful about a commit in relation to
> its preceding history, while at the same time uniquely identifying the
> commit. The "uniquely identifying" part is taken care of by
> the "-g<SHA1>" part of the output, while the initial "<tagname>-<n>"
> part makes it human-friendly. Therefore, we only care that the
> <tagname> is fairly unambiguous in the mind of the reader. From this
> perspective, which of the alternatives makes more sense? I would
> disqualify "$remote/$tag" and "$remote/tags/$tag", since the $remote
> name is repo-specific, and 'describe' output is often passed around
> between multiple developers/repos. Hence, I think that "$tag" is a good
> choice for 'describe'. If "$tag" is ambiguous in the current repo, then
> an "ambiguous tag" tag warning can be printed, but I would still
> use "$tag".
>
> When it comes to 'name-rev' and '--decorate', those are (AFAICS) much
> more repo-specific, and seldom passed between users. Also, they don't
> have the "-g<SHA1>" part from the 'describe' output. Hence, in this
> case, I consider unique identification (unambiguity) much more
> important than not displaying $remote names. Therefore, I'd propose
> using the shortest unambiguous alternative.

I agree. Something like this I had in mind :)


>
>> Another point to consider is if we want a default remote for tags, a
>> config tags.defaultRemote (TBD), defaulting to origin, specifying the
>> default remote for tags. There would be a hierarchy: local tags,
>> default remote tags, remote tags. With this if one tag is on multiple
>> remote the tag from the default remote always wins.
>>
>> In this way all the tag related input/output would no change much.
>> For example all the decoration would be $tag instead of origin/tag.
>
> Agreed, tags.defaultRemote (or tags.preferredRemote if I'm allowed to
> bikeshed) may be a valuable addition. Another way to achieve this would
> be to explicitly copy tags from the preferred remote (e.g. origin)
> directly into refs/tags. I.e. in addition to the (new) default tag
> refspec
>
>        +refs/tags/*:refs/remotes/origin/tags/*
>
> you could add an _additional_ refspec
>
>        refs/tags/*:refs/tags/*
>
> that would also copy all of origin's tags directly into your local tag
> namespace.

Yes, you always can add this refspec but I don't want to pollute my
"strict" local tags. And moreover with the config tags.preferredRemote
you can change from one preferred remote to another just changing a
config.

> Thanks for the feedback! :)

Thanks for the proposal!

HTH,
Santi