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

[Andreas Heiduk <asheiduk@gmail.com>]

Am 22.04.2018 um 13:17 schrieb Ævar Arnfjörð Bjarmason:
> 
> On Sun, Apr 22 2018, Andreas Heiduk wrote:
> 
>> 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:

Its not emergent because "origin" is the other remote responsible for
that ref and cleaning stuff "belonging" to the remote is the job
description (I'm arguing from a user's perspective, not as a git-developer).

> 
>     (
>         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.

Exactly my point: When you are in a the bad situation of "shared
responsibility", then there is no easy and always correct way out,
because there are uncountable possible situations.

To give another, slightly modified example expanding the problem space:

(
    rm -rf /tmp/git &&
    git clone --bare --mirror https://github.com/git/git.git /tmp/git &&
    cd /tmp/git &&
    git remote add github https://github.com/avar/git.git &&
    git fetch github &&
    git fetch origin &&
    # note new fetches for "github/master" using with "(forced update)"
)

For ... reasons the first repo publishes some references like

	github/maint
	github/master
	github/pu

So when this repo is mirrored AND another, suitably named remote is
added then there will be also namespace conflicts. You can call

    git fetch github
    git fetch origin

in a loop and most likely each fetch will update the same refs, always
toggling between two states.

So: not only "remote remove" and "remote prune" are at stake but every
command handling remote references.

How should "git remote remove github" work in both situations? Remove
the refs/remotes/github/master & co? remove them only if the last fetch
was for "github" but not when the last update was for "origin"? Should
"git fetch" use the same logic?

So it seems better to me to avoid that bad situation altogether. Don't
allow overlapping/conflicting refspecs when adding a new remote. Using
*your* last examples both

>         git remote add avar git@github.com:avar/git.git &&
>         git remote add peff git@github.com:peff/git.git &&

should have failed and hence the "prune" problems won't exist. Same for
my example.

>> 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.

Ummm. That was not my point. My is: "git clone --mirror" uses a refspec

	fetch = +refs/*:refs/*

and hence "occupies" the complete "refs/*" namespace. So adding another
remote (for the first time or for the second time is as irrelevant as
the url) will use

	fetch = +refs/heads/*:refs/remotes/peff/*

and now the "refs/remotes/peff/*" part is in conflict with "refs/*" from
above. The conflict exists not only for "prune" or "remove" but also for
"fetch", "rename" (didn't check) .

This kind of conflict should not be allowed right from the start - when
the first "git remote add peff..." is executed. Then prune, remove AND
fetch would be OK.