Re: [PATCH 2/2] remote.c: reject 0-length branch names

[Glen Choo <chooglen@google.com>]

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

> On Tue, May 31 2022, Glen Choo via GitGitGadget wrote:
>
>> From: Glen Choo <chooglen@google.com>
>>
>> Branch names can't be empty, so config keys with an empty branch name,
>> e.g. "branch..remote", are silently ignored.
>>
>> Since these config keys will never be useful, make it a fatal error when
>> remote.c finds a key that starts with "branch." and has an empty
>> subsection.
>
> Perhaps this is fine, but I think this commit message (and I checked the
> CL too) really needs to work a bit harder to convince us that this is
> safe to do.

Fair.

> Are we confident that this is just bizarro config that nobody would have
> had in practice? In that case I think it's fine to start dying on it.
>
> But as I understand we previously just ignored this, then if there's any
> doubt about that perhaps we should start with a warning?
>
> Or are we really confident that this is an edge case not worth worrying
> about in that way, and that we can go straight to die()?

The case I want to make is even stronger than that - this is an edge
case that _we_ shouldn't worry about, and we should tell the _user_ that
their config is bogus.

It truly makes no sense because `branch..remote` fits the schema of
`branch.<name>.remote` where <name> is "", but "" isn't a valid branch
name (and it never has been AFAIK). So such a key would never be useful
to Git, and it would be extremely hacky for a non-Git tool to use such
a key.

I'm not sure how a user would generate such a key in the wild (e.g.
[1]). Maybe it was a typo, but more worryingly (I don't have evidence
for this, but it could happen), it might be misbehavior from `git
[branch|config]` that we never noticed because the bogus keys have flown
under the radar. If there really is a bug elsewhere, erroring out when
we see such keys might also alert us to the bug.

Perhaps I need to capture all of this in the commit message?

[1] https://lore.kernel.org/git/24f547-6285e280-59-40303580@48243747/