Re: refspecs with '*' as part of pattern

[Jacob Keller <jacob.keller@gmail.com>]

On Mon, Jul 6, 2015 at 7:33 PM, Jacob Keller <jacob.keller@gmail.com> wrote:
> On Mon, Jul 6, 2015 at 7:20 PM, Daniel Barkalow
> <barkalow@iabervon.iabervon.org> wrote:
>> 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
>> *This .sig left intentionally blank*
>
>
> Which is why I suggested a patch that adds this behavior conditionally
> and only for fetch. This way you don't have to use a local patch, and
> it wouldn't hit normal users. Ideally we can add a flag that only
> enables it for refspecs that don't interoperate.
>
> Does this seem ok? If so I will go ahead and try to work up a patch
>
> Regards,
> Jake

I am working up a patch to try and get this configurable. I'll
hopefully send it out tomorrow morning sometime.

Regards,
Jake