Guix Authenticate confusing behavior

[Jodi Jodington (dev)]

Hello guix! I recently had trouble with `guix git authenticate`'s default 
behavior of
placing a hook to your git repository to re-run `guix git authenticate` 
every time you push and was wondering
if it was worth re-considering. In my case, I was contributing to guix so 
I made a fork of the
official repo on codeberg and followed 'Building from Git' from the guix 
manual which told me to run
`guix git authenticate` after pulling the repo. I then proceeded to make 
a change and commit it locally
and then tried to push it to my fork. This resulted in an error message 
about how my commit
isn't signed and blocked me from pushing. The solution here is to delete 
the .git/hooks/pre-push
that `guix git authenticate` created, but it took a while to figure it 
out and it was quite confusing.
It was quite discouraging to me that following the official instructions 
wasn't enough to contribute to guix.
It would be nice if the manual warned you that if you were doing this 
with a fork, you should look at
the `Invoking Guix Authenticate` chapter of the guix manual to see how to 
add your GPG key
as a valid signature for your branch (or suggest deleting the pre-push 
hook if you don't care).

I also think that `guix git authenticate` creating a git hook without
any prompting or explicit arguments is pretty invasive behavior in 
general and
doesn't really justify itself. I would prefer it if you had to do 
something like
`guix git authenticate --add-hook` or similar (or just have users create 
the hook themselves, it isnt a big deal imo)