Jeff King <peff@xxxxxxxx> writes:
> On Mon, Jul 17, 2017 at 10:27:09AM -0700, Jonathan Nieder wrote:
>> ...
>> 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.
> So any script calling "check-ref-format --branch" outside of a repo
> would be better off not calling it at all.
I threw this topic in stalled category, hoping that one or the other
opinion eventually turns out to be more prevalent, but it didn't
seem to have happened X-<.
Things like @{-1} would not make any sense when the command is run
outside a repository, and the documentation is quite clear that it
is the primary reason why we added "--branch" option to the command,
i.e.
With the `--branch` option, it expands the ``previous branch syntax''
`@{-n}`. For example, `@{-1}` is a way to refer the last branch you
were on. This option should be used by porcelains to accept this
syntax anywhere a branch name is expected, so they can act as if you
typed the branch name.
So I am tempted to take this patch to make sure that we won't gain
more people who abuse the command outside a repository.
Having said that, there may still be a use case where a Porcelain
script wants a way to see if a $name it has is appropriate as a
branch name before it has a repository (e.g. a wrapper to "git
clone" that wants to verify the name it is going to give to the "-b"
option), and a check desired in such a context is different from
(and is stricter than) feeding refs/heads/$name to the same command
without the "--branch" option.
So I think the right endgame in the longer term is:
- Find (or add if it doesn't exist) a way to recommend to Porcelain
scripts to use to expand an end-user generated string, and to map
it to a branch name (it may be "rev-parse --symbolic-full-name
$name"; I dunno).
- Keep check-ref-format as (or revert it to be) a tool to "check".
This would involve split strbuf_check_branch_ref() into two:
- one that does not do the @{-1} thing and is used ONLY for
format validity check (including rejecting a name that begins
with a dash, which is OK for a random ref but not acceptable as
a branch name);
- the other that does @{-1} thing before doing the above.
and then making the code call the former, not the latter.
The end result would be that check-ref-format becomes textual check
only, and can be usable (agian) outside repository, with or without
"--branch". As the current code does not allow us do that yet, I
think it is safer to forbid use of --branch outside the repository
for now, purely as a bugfix.
[Footnote]
*1* In a sense, @{-1} is not something the scripts need to check its
validity of---it is the branch you came from, so by definition
it must be with a good name. What the scripts want is instead
see what the branch actually is, which is not what
"check-ref-format" is about.
a31dca03 ("check-ref-format --branch: give Porcelain a way to
grok branch shorthand", 2009-03-21) says:
The command may not be the best place to add this new feature, but
$ git check-ref-format --branch "@{-1}"
allows Porcelains to figure out what branch you were on before the last
branch switching.
