Re: [PATCH] t6300: avoid creating refs/heads/HEAD

[Jeff King <peff@peff.net>]

On Mon, Feb 27, 2017 at 01:19:29PM -0800, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > I suspect there are a lot of other places that are less clear cut. E.g.,
> > I think just:
> >
> >   git branch foo bar
> >
> > will put "foo" through the same interpretation. So you could do:
> >
> >   git branch -f @{-1} bar
> >
> > Is that insane? Maybe. But it does work now.
> 
> No, it _is_ very sensible, so is "git checkout -B @{-1} <someplace>"
> 
> Perhaps interpret-branch-name that does not error out when given "@"
> is what is broken?  I suspect that calling interpret_empty_at() from
> that function is fundamentally flawed.  The "@" end user types never
> means refs/heads/HEAD, and HEAD@{either reflog or -1} would not mean
> anything that should be taken as a branch_name, either.
> 
> So perhaps what interpret_empty_at() does is necessary for the "four
> capital letters is too many to type, so just type one key while
> holding a shift", but it should be called from somewhere else, and
> not from interpret_branch_name()?

I think _most_ of interpret_branch_name() is in the same boat. The
"@{upstream}" mark is not likely to give you a branch in refs/heads
either.

So in practice, I think strbuf_check_branch_ref() could probably get by
with just calling interpret_nth_prior_checkout(). Or if you prefer, to
rip everything out of interpret_branch_name() except that. :) But that
other stuff has to go somewhere, and there are some challenges with the
recursion from reinterpret().

The "other" stuff could sometimes be useful, I guess. It's not _always_
wrong to do:

  git branch -f @{upstream} foo

It depends on what your @{upstream} resolves to. Switching to just using
interpret_nth_prior_checkout() would break the case when it resolves to
a local branch. I'm not sure if we're OK with that or not. If we want to
keep all the existing cases working, I think we need something like the
"not_in_refs_heads" patch I posted elsewhere.

-Peff