Re: [PATCH 2/2] describe: Exclude --all --match=PATTERN

From: Greg Price <price@mit.edu>
Date: Mar 3, 2013, 22:07 UTC
Message-ID: <20130303220756.GN22203@biohazard-cafe.mit.edu>
In-Reply-To: <7vfw0cb2xi.fsf@alter.siamese.dyndns.org>

On Sun, Mar 03, 2013 at 01:15:21PM -0800, Junio C Hamano wrote:

Show 16 quoted lines

> Greg Price <price@MIT.EDU> writes:
> > It seems to me that "--all" says two things:
> >
> >  (a) allow unannotated (rather than only annotated)
> >
> >  (b) allow refs of any name (rather than only tags)
> >
> > With "--match", particularly because the pattern always refers only to
> > tags, (b) is obliterated, and your proposed semantics are (a) plus a
> > sort of inverse of (b):
> >
> >  (c) allow only refs matching the pattern
> 
> I would think it is more like "only (a), without changing the
> documented semantics of what '--all' and '--match' are by adding (b)
> or (c)".

Perhaps I'm confused somehow? I believe (a) and (b) together are the documented semantics of what '--all' is. And I believe (c), which contradicts (b) and indeed goes in the opposite direction, is the documented semantics of what '--match' is.

Certainly we could choose to resolve the conflict by saying that '--match' overrides '--all', so that '--all' plus '--match' means (a)+(c). I believe that's what you suggested.

I think it would be preferable to recognize the conflict and let the user sort out what they actually mean, because if they (or their script) gave these options together then I think there's a substantial likelihood that they are confused or their script is buggy. If they mean (a)+(c), they can get it more clearly with '--tag --match'.

Show 6 quoted lines

> I do not think in the longer term it is wrong per-se to change the
> semantics of "--match" from the documented "Only consider tags
> matching the pattern" to "Only consider refs matching the pattern",
> and such a change can and should be made as a separate patch
> "describe: loosen --match to allow any ref, not just tags" on top of
> the patch I sent which was meant to be bugfix-only.

Yeah, that could be useful. What form of pattern would you suggest that the new '--match' accept? The obvious, and unambiguous, form of pattern is glob patterns on the full ref name, as with 'for-each-ref'. Those are a little unwieldy for interactive use, but are perfect for a script. And probably 'describe --match' itself already makes the most sense in a scripted context, as for interactive use one can go into 'gitk' or 'git log --oneline --decorate' or the like and find out the same information plus more detail.

Particularly when handling both tags and other refs, I can also imagine wanting to specify a disjunction of several patterns. So we might want to accept the option several times cumulatively.

I'd worry about changing the semantics of existing 'describe --match' invocations in people's scripts, etc. Perhaps we'd give it a new name like '--match-ref'. Or we could say something like, if it starts with "refs/" it's a pattern on the whole refname, else it's a pattern on just the tag name, and accept that if someone has a ref called "refs/tags/refs/foo" and was finding it with 'describe --match' then that will break until they edit the pattern.

Cheers, Greg