Re: [PATCH] check-ref-format: require a repository for --branch

[Junio C Hamano <gitster@pobox.com>]

Jeff King <peff@peff.net> writes:

> On Mon, Jul 17, 2017 at 10:27:09AM -0700, Jonathan Nieder wrote:
>
>> > --- a/t/t1402-check-ref-format.sh
>> > +++ b/t/t1402-check-ref-format.sh
>> > @@ -161,6 +161,10 @@ test_expect_success 'check-ref-format --branch from subdir' '
>> >  	test "$refname" = "$sha1"
>> >  '
>> >  
>> > +test_expect_success 'check-ref-format --branch from non-repo' '
>> > +	test_must_fail nongit git check-ref-format --branch @{-1}
>> > +'
>> > +
>> >  valid_ref_normalized() {
>> >  	prereq=
>> >  	case $1 in
>> 
>> I don't think it's right.  Today I can do
>> 
>> 	$ cd /tmp
>> 	$ git check-ref-format --branch master
>> 	master
>> 
>> You might wonder why I'd ever do such a thing.  But that's what "git
>> check-ref-format --branch" is for --- it is for taking a <branch>
>> argument and turning it into a branch name.  For example, if you have
>> a script with an $opt_branch variable that defaults to "master", it
>> may do
>> 
>> 	resolved_branch=$(git check-ref-format --branch "$opt_branch")
>> 
>> even though it is in a mode that not going to have to use
>> $resolved_branch and it is not running from a repository.
>
> I'm not sure I buy that. What does "turning it into a branch name" even
> mean when you are not in a repository? Clearly @{-1} must fail. And
> everything else is just going to output the exact input you provided.

This "just going to output the exact input" is not entirely correct;
there is just one use case for it.

"git check-ref-format --branch a..b" would fail with a helpful error
message, while the command run with "a.b" would tell you the name is
safe.

Use of 'check-ref-format --branch "@{-1}"' *IS* a nonsense, whether
it is inside or outside a repository; it is OK to fail it outside a
repository and I would say it is even OK to fail it inside a
repository.  After all "check-ref-format" is about checking if the
string is a sensible name to use.

I think calling interpret_branch_name() in the codepath is a mistake
and we should instead report if "refs/heads/@{-1}" literally is a
valid refname we could create instead.