Re: [PATCH 0/7] Make "$remote/$branch" work with unconventional refspecs

From: Johan Herland <johan@herland.net>
Date: May 6, 2013, 23:42 UTC
Message-ID: <CALKQrgeegzzJ-2QNvdmeeugS0Aw7jrE4SM8S7zk+qPdfgRCMyg@mail.gmail.com>
In-Reply-To: <7vhaigrqay.fsf@alter.siamese.dyndns.org>

On Mon, May 6, 2013 at 7:06 PM, Junio C Hamano <gitster@pobox.com> wrote:

Show 19 quoted lines

> Johan Herland <johan@herland.net> writes:
>> Let me try to summarize my views on how refnames should work in Git, to
>> see if we can identify where we differ on the principles (or if we, in
>> fact, differ at all):
>
> Thanks; I think I already said where I think we differ in a separate
> message, but a short version is that the point of remote.$nick.fetch
> mapping is to solve "The remote may call a ref $this, which is not
> the refname I want to or can use in my repository, so here is the
> rule to use when importing it in my local namespace.  With the
> mapping, I can name the ref in my local namespace conveniently."
> E.g. their "refs/heads/master" cannot be our "refs/heads/master" at
> the same time, so use "refs/remotes/origin/master".
>
> The result of the above mapping, be it remotes/origin/master or
> remotes/origin/heads/master, should be designed to be useful for the
> local use of the ref in question.  If you further need to remap it
> when using it locally, there is something wrong in the mapping you
> defined in your remote.$nick.fetch mapping in the first place.

Ok, so whereas I consider the refspec to be "king", and that the expansion from convenient shorthands to full remote-tracking refnames should be derived from the chosen refspec, you would (if I understand you correctly) rather have a constant (i.e. independent of remotes and refspecs) set of rules for expanding shorthands to full refnames, and if the user chooses refspecs that don't mesh well with those rules, then that is the user's problem, and not Git's.

> We do not force any structure under refs/remotes/; it is left
> entirely up to the user, even though we would like to suggest the
> best current practice by teaching "clone" and "remote add" to lay
> them out in a certain way.

If we were to suggest +refs/heads/*:refs/remotes/origin/heads/* as the best practice, I assume you do want "origin/master" to keep working. And since you do not want to use the configured refspec when expanding "origin/master" into "refs/remotes/origin/heads/master", then I assume you would rather add a hardcoded (what I call a "textual expansion" in my patches) rule that would map "$nick/$name" into

  /refs/remotes/$nick/heads/$name

But isn't the existence of such a rule evidence of us trying to impose (or at least hint) at a certain structure for refs/remotes/*?

In light of this, I'm interested in your thoughts about the following related problem that I've just started looking at:

git branch -r shows the remote-tracking branches in this repo. Currently, AFAICS, this just spits out all refs under refs/remotes/*. This behavior must clearly be modified if we are to allow remote-tracking tags at refs/remotes/$remote/tags/* (they currently show up in "git branch -r", but shouldn't). One could say that the filter should merely change from refs/remotes/* to refs/remotes/*/heads/*, but this would break for existing (old-style) remotes. Should we add a heuristic for detecting when to use refs/remotes/* vs. refs/remotes/*/heads/* as a filter?

My approach would be to iterate through the configured remotes, and for each remote list all refs that match the RHS of the refspec whose LHS is refs/heads/*. This would work for both old- and new-style remotes with no heuristics.

If you agree that my approach is correct for enumerating remote-tracking branches, then what is different about using the refspec when expanding remote-tracking refs in general?

In other words, given the following configuration:

  [remote "origin"]
          +refs/heads/*:refs/foo/bar/baz/*
  [remote "foo"]
          +refs/heads/*:refs/remotes/origin/heads/*

1. In your opininon, is refs/foo/bar/baz/master a remote-tracking branch?

2. Should refs/foo/bar/baz/master be listed by "git branch -r"?

3. Should the "origin/master" shorthand notation expand to
   refs/remotes/origin/heads/master from remote foo, or
   refs/foo/bar/baz/master from remote origin?

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net