Re: RFC: How should we handle un-deleted remote branches?

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Apr 22, 2018, 11:17 UTC
Message-ID: <87d0yrebhw.fsf@evledraar.gmail.com>
In-Reply-To: <3fcd1b50-2aeb-0ea4-fea7-b5705e76c027@gmail.com>

On Sun, Apr 22 2018, Andreas Heiduk wrote:

Show 11 quoted lines

> Am 20.04.2018 um 14:14 schrieb Ævar Arnfjörð Bjarmason:
>> But this is a possible work-around:
>>
>>     git init /tmp/empty.git
>>     git remote add avar file:///tmp/empty.git
>>     git remote prune avar
>>     git remote remove avar
>
> This won't do it also?
>
> 	git remote prune origin

Yes, in this particular case, but that's just emergent behavior in how we handle refspec prunign, and the fact that it "works" is arguably a bug in "prune". i.e. this:

    (
        rm -rf /tmp/git &&
        git clone --bare --mirror git@github.com:git/git.git /tmp/git &&
        cd /tmp/git &&
        git remote add avar git@github.com:avar/git.git &&
        git remote add peff git@github.com:peff/git.git &&
        git fetch --all &&
        git remote remove avar &&
        git remote prune origin
    )

Will delete all the avar/* and peff/* branches, even though I still have a "peff" remote.

IOW the guarding logic we have in add_branch_for_removal() for not deleting the branches of other remotes isn't in the corresponding "prune" function, and that's a bug.

In the specific example I picked "git remote prune origin" just so happens to do the right thing since I have no other active remote, and there *is* an alive remote so I can "prune" against it, but it doesn't help in the general case. In my case I have a remote URL for a git server called "upstream" that doesn't exist anymore (but as noted, I can fake it with an empty repo...)>

Show 31 quoted lines

>> I started to patch this, but I'm not sure what to do here. we could do
>> some combination of:
>>
>>  0. Just document the current behavior and leave it.
>>
>>  1. Dig further down to see what other remotes reference these refs, and
>>     just ignore any refspecs that don't explicitly reference
>>     refs/remotes/<our_deleted_remote>/*.
>>
>>     I.e. isn't the intention here to preserve a case where you have two
>>     URLs for the same effective remote, not whene you have something
>>     like a --mirror refspec? Unfortunately I can't ask the original
>>     author :(
>>
>>  2. Warn about each ref we didn't delete, or at least warn saying
>>     there's undeleted refs under refs/remotes/<name>/*.
>>
>>  3. Make 'git remote remove --force-deletion <name>' (or whatever the
>>     flag is called) be a thing. But unless we do the next item this
>>     won't be useful.
>>
>>  4. Make 'git remote prune <name>' work in cases where we don't have a
>>     remote called <name> anymore, just falling back to deleting
>>     refs/remotes/<name>. In this case 'git remote remove
>>     --force-deletion <name>' would also do the same thing.
>
> Possible 5):
>
> 	Don't fix "git remote remove" but "git remote add" to complain that its
> ref-namespace is already occupied by some other remote. Add "--force"
> for the experts.

Indeed, that's another bug here, i.e. in the above example:

    git remote remove peff && # won't delete peff/ branches
    git remote add peff git@github.com:peff/git.git

Will happily add the "peff" remote again, even though as you point out it could be an entirely different remote.