Re: refspecs with '*' as part of pattern

[Daniel Barkalow <barkalow@iabervon.iabervon.org>]

On Mon, 6 Jul 2015, Junio C Hamano wrote:

> Jacob Keller <jacob.keller@gmail.com> writes:
> 
> > I've been looking at the refspecs for git fetch, and noticed that
> > globs are partially supported. I wanted to use something like:
> >
> > refs/tags/some-prefix-*:refs/tags/some-prefix-*
> >
> > as a refspec, so that I can fetch only tags which have a specific
> > prefix. I know that I could use namespaces to separate tags, but
> > unfortunately, I am unable to fix the tag format. The specific
> > repository in question is also generating several tags which are not
> > relevant to me, in formats that are not really useful for human
> > consumption. I am also not able to fix this less than useful practice.
> >
> > However, I noticed that refspecs only support * as a single component.
> > The match algorithm works perfectly fine, as documented in
> > abd2bde78bd9 ("Support '*' in the middle of a refspec")
> >
> > What is the reason for not allowing slightly more arbitrary
> > expressions? Obviously no more than one *...
> 
> I cannot seem to be able to find related discussions around that
> patch, so this is only my guess, but I suspect that this is to
> discourage people from doing something like:
> 
> 	refs/tags/*:refs/tags/foo-*
> 
> which would open can of worms (e.g. imagine you fetch with that
> pathspec and then push with refs/tags/*:refs/tags/* back there;
> would you now get foo-v1.0.0 and foo-foo-v1.0.0 for their v1.0.0
> tag?) we'd prefer not having to worry about.

That wouldn't be it, since refs/tags/*:refs/tags/foo/* would have the same 
problem, assuming you didn't set up the push refspec carefully.

I think it was mostly that it would be too easy to accidentally do 
something you don't want by having some other character instead of a 
slash, like refs/heads/*:refs/heads-*.

Aside from the increased risk of hard-to-spot typos leading to very weird 
behavior, nothing actually goes wrong; in fact, I've been using git with 
that check removed for ages because I wanted a refspec like 
refs/heads/something-*:refs/heads/*. And it works fine as a local patch, 
since you don't need your refspec handling to interoperate with other 
repositories.

	-Daniel
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