Re: [1.8.0] Provide proper remote ref namespaces

On Mon, 14 Feb 2011, Johan Herland wrote:

On Monday 14 February 2011, Junio C Hamano wrote:

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Johan Herland [off-list ref] writes:

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Yes, replicating existing behavior w/explicit refspecs would look like: 
  [remote "origin"]
  
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD

Perhaps

              setHead = master

or something like that?

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        fetch = +refs/heads/*:refs/remotes/origin/*
        fetch = ~refs/tags/*:refs/tags/*

While this is fine, I am not sure about the "HEAD" part.  Most of the
protocol do not convey which branch HEAD points at (instead "clone" has
to guess), which eventually needs to be fixed.

Right.

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Incremental updates via 
"fetch" does not touch "HEAD" at all by design; unlike the real branch
heads "remotes/origin/$branch" that are used to keep copies of what are
at the remote, "remotes/origin/HEAD" is meant to be used by the local
repository to designate which of the remote branch is considered the
primary branch from local repository owner's point of view, primarily so
that you can say "origin" locally to mean "origin/next" by setting the
symref origin/HEAD to point at it.  In that sense, the guess made by
"clone" is only used to give an initial value.

Well, we have "git remote set-branch <remote> -a" to re-do this guessing
or checking, and update 'remotes/origin/HEAD'...

Ah, ok. I've misunderstood the purpose of "remotes/origin/HEAD" then. Feel 
free to remove that refspec line from my proposal, and leave it as a 
special-purpose thing set up by clone (and maintained by the user 
thereafter).

See above for my `remote.<remote>.setHead` proposal.

Still (as I think was recently discussed in another thread), the existence 
of remotes/origin/HEAD _does_ cause problems if the origin remote also has a 
branch called "refs/heads/HEAD" (which would collide when fetched into the 
local repo).

True, though... can't we consider having branch named 'HEAD' as insane?

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FTR, my new/proposed refspecs would look like this:
  [remote "origin"]
  
        url = git://git.example.com/repo.git
        fetch = +HEAD:refs/remotes/origin/HEAD
        fetch = +refs/heads/*:refs/remotes/origin/heads*
        fetch = ~+refs/tags/*:refs/remotes/origin/tags/*
      
      ( fetch = +refs/notes/*:refs/remotes/origin/notes/* )
      ( fetch = +refs/replace/*:refs/remotes/origin/replace/* )

I think you meant "refs/remotes/origin/heads/*" (note the slash) on the
RHS of the branch refspecs.

Indeed. Thanks for pointing out the typo.

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How's that different from refs/*:refs/remotes/origin/* by the way?

It's not, except that "refs/*:refs/remotes/origin/*" would fetch a too-large 
superset. E.g. it would fetch "refs/remotes/third-party/heads/foo" into 
"refs/remotes/origin/remotes/third-party/heads/foo", which we probably don't 
want.

Note that it is not given that notes and replaces should be per-remote
like remote-tracking branches, and not autofollowed like tags.

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Also
if you give tags a totally separate namespace, I don't see much reason to
still give it the "auto-follow" semantics.  It is far simpler to explain
if you just fetch all of them and be done with it, no?

Agreed. Also, to quote Peff in http://thread.gmane.org/gmane.comp.version-
control.git/160503/focus=160726 :

"Now you could argue that auto-follow is not worth the effort. It is
somewhat confusing, and I can't think of a time when it ever actually
reduced the set of objects I was fetching (as opposed to just fetching
all tags). But maybe others have use cases where it matters."

So if nobody disagree, I would have no problem with dropping the leading "~" 
from the refspec, thus disabling auto-following (tracking all tags 
explicitly instead).

Well, to make use of somewhat contrived example: with current auto-follow
fetching of tags, when somebody tracks e.g. only 'maint' branch, he/she
wouldn't get "*-rcN" tags he/she is not interested in.

Worth preserving?

[...] 

I don't doubt that the current behavior works well for you (otherwise I 
expect you would have changed it). However, what I've seen at $dayjob is 
that more inexperienced users will often push right after committing, and at 
that time they're still very much in the "working-on-one-branch" state of 
mind (as opposed to the "administering-multiple-branches" state of mind), so 
when they follow up a "git commit" with a "git push" they're surprised (or 
worse: oblivious) to the fact that "git push" can push multiple branches.

I guess it comes down to whether you fundamentally consider "git push" 
something that pushes multiple _branches_, or something that pushes multiple 
_commits_. And for the latter of those groups push.default == "matching" is 
inherently more "dangerous" than for the former. (Granted, me telling 
everyone to use push.default == "tracking" probably doesn't help them in 
discovering "git push"'s ability to update multiple branches.)

Another solution is to tech them "topic branch" workflow, i.e. to do new
work on new feature branch, and only when it is ready merge it into one
of published branches (i.e. those that have matching branch in remote 
repository they push to).

-- 
Jakub Narebski
Poland