Re: [PATCH] ref-filter: don't look for objects when outside of a repository

["SZEDER Gábor" <szeder.dev@gmail.com>]

On Fri, Nov 16, 2018 at 02:09:07PM +0900, Junio C Hamano wrote:
> Jeff King <peff@peff.net> writes:
> 
> > On Thu, Nov 15, 2018 at 04:38:44AM -0500, Jeff King wrote:
> >
> >> Is SOURCE_NONE a complete match for what we want?
> >> 
> >> I see problems in both directions:
> >> 
> >>  - sorting by "objectname" works now, but it's marked with SOURCE_OBJ,
> >>    and would be forbidden with your patch.  I'm actually not sure if
> >>    SOURCE_OBJ is accurate; we shouldn't need to access the object to
> >>    show it (and we are probably wasting effort loading the full contents
> >>    for tools like for-each-ref).
> >> 
> >>    However, that's not the full story. For objectname:short, it _does_ call
> >>    find_unique_abbrev(). So we expect to have an object directory.
> >
> > Oops, I'm apparently bad at reading. It is in fact SOURCE_OTHER, which
> > makes sense (outside of this whole "--sort outside a repo thing").
> >
> > But we'd ideally distinguish between "objectname" (which should be OK
> > outside a repo) and "objectname:short" (which currently segfaults).
> 
> Arguably, use of ref-filter machinery in ls-remote, whether it is
> given from inside or outside a repo, was a mistake in 1fb20dfd
> ("ls-remote: create '--sort' option", 2018-04-09), as the whole
> point of "ls-remote" is to peek the list of refs and it is perfectly
> normal that the objects listed are not available.

I hope that one day 'git ls-remote' will learn to '--format=...' its
output, and I think that (re)using the ref-filter machinery would be
the right way to go to achive that.  Sure, ref-filter supports a lot
of format specifiers that don't at all make sense in the context of
'ls-remote' (perhaps we should have a dedicated set of valid_atoms for
that), but I think it's perfectly reasonable to do something like:

  git ls-remote --format=%(refname:strip=2) remote

A concrete use case for that could be to eliminate the last remaining
shell loops from refs completion.