Re: check-ref-format: include refs/ in the argument or to strip it?

On Fri, Aug 22, 2014 at 10:46 PM, Jeff King [off-list ref] wrote:

On Fri, Aug 22, 2014 at 11:45:15AM -0700, Jonathan Nieder wrote:

quoted

Junio C Hamano wrote:

quoted

               implication of which is that the 'at least one slash'
rule was to expect things are 'refs/<anything>' so there will be at
least one.  Even back then, that <anything> alone had at least one
slash (e.g. heads/master), but the intention was *never* that we
would forbid <anything> that does not have a slash by feeding
<anything> part alone to check-ref-format, i.e. things like
"refs/stash" were designed to be allowed.

Now I'm more confused.  Until 5f7b202a (2008-01-01), there was a
comment

              if (level < 2)
                      return -2; /* at least of form "heads/blah" */

and that behavior has been preserved since the beginning.

Why do most old callers pass a string that doesn't start with refs/
(e.g., see the callers in 03feddd6, 2005-10-13)?  Has the intent been
to relax the requirement since then?

Yeah, this weird "do not allow refs/foo" behavior has continually
confused me. Coincidentally I just noticed a case today where
"pack-refs" treats "refs/foo" specially for no good reason:

  http://thread.gmane.org/gmane.comp.version-control.git/255729

After much head scratching over the years, I am of the opinion that
nobody every really _meant_ to prevent "refs/foo", and that code
comments like the one you quote above were an attempt to document
existing buggy behavior that was really trying to differentiate "HEAD"
from "refs/*". That's just my opinion, though. :) I'd be happy if all of
the special-treatment of "refs/foo" went away and check_refname_format
always got the full ref.

There are also a lot of places where we assume that a refs will start
with "refs/heads/" and not just "refs/"
for_each_branch_ref(), log_ref_setup() (so no reflogs) is_branch() to
name a few.

This makes the api a bit confusing and hard to predict. Which
functions allow refs/foo and which will ignore it?
Are there any compelling reasons why refs/foo should be allowed?