Re: [PATCH 0/3] object-name: don't allow @ as a branch name

["Kristoffer Haugsbakk" <code@khaugsbakk.name>]

On Tue, Oct 8, 2024, at 15:19, shejialuo wrote:
> On Mon, Oct 07, 2024 at 10:15:16PM +0200, Kristoffer Haugsbakk wrote:
>
> [snip]
>
>>   §2 Disallow `HEAD` as a branch name
>> 
>> This was done later in 2017:
>> 
>> https://lore.kernel.org/git/20171114114259.8937-1-kaartic.sivaraam@gmail.com/
>> 
>>   §2 `refs/heads/@` is apparently disallowed by git-refs(1)
>> 
>> See `t/t1508-at-combinations.sh`:
>> 
>> ```
>> error: refs/heads/@: badRefName: invalid refname format
>> ```
>> 
>
> It's true that using "git refs verify" will report "refs/heads/@" is a
> bad refname.
>
> From the man page of the "git-check-ref-format(1)", it is clear that
>
>     9. They cannot be the single character @.
>
> Because I am interesting in this patch which is highly relevant with my
> recent work, so I try somethings here and find some interesting results
> as below shows.
>
>     $ git check-ref-format refs/heads/@
>     $ echo $? # will be 0
>     # git check-ref-format --allow-onelevel @
>     # echo $? # will be 1
>
> The reason why "git refs verify" will report this error is that in the
> code implementation, I have to iterate every file in the filesystem. So
> it's convenient for me to do the following:
>
>     if (check_refname_format(iter->basename, REFNAME_ALLOW_ONELEVEL)) {
>         ret = fsck_report(...);
>     }
>
> Because I specify "REFNAME_ALLOW_ONELEVEL" here, so it will follow the
> "git check-ref-format --allow-onelevel" command thus reporting an error
> to the user.
>
> I am curious why "git check-ref-format refs/heads/@" will succeed, so I
> try to use "git symbolic-ref" and "git update-ref" to verify to test the
> behavior.
>
>     $ git symbolic-ref refs/heads/@ refs/heads/master
>     error: cannot lock ref 'refs/heads/@': unable to resolve reference 
> 'refs/heads/@': reference broken
>     $ git update-ref refs/heads/@ refs/heads/master
>     fatal: update_ref failed for ref 'refs/heads/@': cannot lock ref 
> 'refs/heads/@': unable to resolve reference 'refs/heads/@': reference 
> broken
>
> So, we are not consistent here. I guess the reason why "git
> check-ref-format refs/heads/@" will succeed is that we allow user create
> this kind of branch.
>
> If we decide to not allow user to create such refs. We should also
> change the behavior of the "check_refname_format" function. (I am not
> familiar with the internal implementation, this is my guess)
>
> Thanks,
> Jialuo

Thanks for the careful analysis.