Re: [PATCH 1/2] ref-filter: hacky "streaming" mode

[ZheNing Hu <adlternative@gmail.com>]

Jeff King <peff@peff.net> 于2021年9月17日周五 上午5:45写道：
>
> On Wed, Sep 15, 2021 at 10:23:43PM +0800, ZheNing Hu wrote:
>
> > ZheNing Hu <adlternative@gmail.com> 于2021年9月15日周三 下午8:27写道：
> > >
> > > > So yes, it's complicated. And it must be explained to the user that
> > > > "%(refname)" behaves slightly differently with "git tag --verify", but
> > > > that is unavoidable if we do not want to break scripts (it _already_
> > > > behaves slightly differently, and we just never told anyone).
> > > >
> >
> > $ git tag --verify --format='verify: %(refname) %(symref)' annotated symref
> > verify: annotated
> > verify: symref
> > $ git tag --verify --format='verify: %(refname) %(symref)'
> > refs/tags/annotated refs/tags/symref
> > error: tag 'refs/tags/annotated' not found.
> > error: tag 'refs/tags/symref' not found.
>
> This is expected. When you provide a tag name on the command line of
> "git tag" it is assumed to be a non-qualified name in refs/tags/ (and
> ditto for git-branch and refs/heads/). It is tempting to try to be
> friendly and accept fully-qualified refs there, but it would create
> ambiguities (e.g., you could really have refs/tags/refs/tags/foo as a
> ref).
>

Yeah, maybe you are right, for git tag --verify, there may have ambiguities.
But for git verify-tag, if we have tags like "refs/tags/refs/tags/foo" and
"refs/tags/foo":

$ git verify-tag --format='verify: %(refname) %(symref)' refs/tags/foo
warning: refname 'refs/tags/foo' is ambiguous.

We see the ambiguities too here.

> I think we can ignore that for our purposes here, though. It's a
> question of input from the command-line, and we focus on just the output
> that we produce.
>

Yeah, but using different functions (read_ref_full(), get_oid()) will
affect what
kind of input we can provide.

> > $ git verify-tag --format='verify: %(refname) %(symref)' annotated
> > symref
> > verify: annotated
> > verify: symref
> > $ git verify-tag --format='verify: %(refname) %(symref)'
> > refs/tags/annotated refs/tags/symref
> > verify: refs/tags/annotated
> > verify: refs/tags/symref
> >
> > As we can see, there is a slight difference between git tag --verify and
> > git verify-tag: git tag --verify can not handle refs' fullname refs/tags/*
> > (because read_ref_full() | read_ref() can't handle them). So, as a standard,
> > which characteristics should we keep?
>
> Whereas are you notice here, verify-tag takes any name (which could be
> fully qualified), and uses it as-is. In fact, it might not even be a ref
> at all! You can say "git verify-tag c06b72d02" if you want to. And as a
> plumbing tool, we should make sure this continues to work. For example,
> careful scripts may resolve a ref into an object, and want to continue
> talking about that object without worrying about the ref being changed
> simultaneously.
>

Yes, this feature is very bad. %(refname) seems to do the %(objectname)
work.


> But it also creates a weirdness for "git verify-tag --format". We do not
> necessarily even have a ref to show. So IMHO the feature is somewhat
> mis-designed in the first place. But we should probably continue to
> support it as best we can.
>
> The best I can come up with is:
>
>   - when we resolve the name, if it was a ref, we should record that.
>     I think this is hard to do now. It would probably require
>     get_oid_with_context() learning to report on the results it got from
>     dwim_ref().
>
>   - if we have a refname, then feed it to pretty_print_ref() as a
>     fully-qualified name. And pass whatever "default lstrip=2" magic we
>     come up with for "git tag --verify". That would mean that "git
>     verify-tag --format=%(refname) v2.33.0" would behave the same before
>     and after.
>
>   - if we didn't get a refname, then...I guess continue to pass the name
>     the user gave us into pretty_print_ref()? That would keep "git
>     verify-tag --format=%(refname) c06b72d02" working as it does today.
>
> The alternative is to do none of those things, and just document that
> "verify-tag" is weird:
>
>   - its %(refname) reports whatever you gave it, whether it is a ref or
>     not
>
>   - some advanced format placeholders like %(symref) may not work if you
>     don't pass a fully-qualified ref
>
> -Peff

This is my solution according to your above suggection:
https://lore.kernel.org/git/pull.1042.git.1632123476.gitgitgadget@gmail.com/

Thanks.
--
ZheNing Hu