Re: [RFC PATCH 1/1] Teach remote add the --prefix-tags option

[Junio C Hamano <gitster@pobox.com>]

Wink Saville <wink@saville.com> writes:

> When --prefix-tags is passed to `git remote add` the tagopt is set to
> --prefix-tags and a second fetch line is added so tags are placed in
> a separate hierarchy per remote.


In the olden days, there was no refs/remotes/$remoteName/ hiearchy,
and until we made it the default at around Git 1.5.0, such a modern
layout for the branches were called the "separate remote" layout,
and can be opted into with "clone --use-separate-remote" by early
adopters.

I doubt that use of refs/tags/$remoteName/ is a good design if we
want to achieve similar isolation between local tags and and tags
obtained from each remote.

An obvious alternative, refs/remotes/$remoteName/tags/, is not a
good design for exactly the same reason.  You cannot tell between a
local tag foo/bar and a tag bar obtained from remote foo when you
see refs/tags/foo/bar, and you cannot tell between a branch tag/bar
obtained from remote foo and a tag bar obtained from remote foo when
you see refs/remotes/foo/tags/bar.  In the past, people suggested to
use refs/remoteTags/$remoteName/ for proper isolation, and it might
be a better middle-ground than either of the two, at least in the
shorter term, but not ideal.

In short, if you truly want to see "separate hierarchy per remote",
you should consider how you can reliably implement an equivalent of
"git branch --list --remote"; a design that does not allow it is a
failure.

A better solution with longer lifetime would probably be to use

	refs/remotes/$remoteName/{heads,tags,...}/

when core.useTotallySeparateRemote configuration exists (and
eventually at Git 3.0 make the layout the default).  It would
involve changes in the refname look-up rules, but it would not have
to pollute refs/ namespace like the refs/remoteTags/ half-ground
design, which would require us to add refs/remoteNotes/ and friends,
who knows how many more we would end up having to support if we go
that route.

Thanks.