bug#45187: git download defaults to origin/master

[Kyle Meyer <kyle@kyleam.com>]

Marius Bakke writes:

> Kyle Meyer <kyle@kyleam.com> skriver:
>
>> One option may be to use the remote HEAD symref.
[...]
>> Here's a quick and dirty demo that makes your reproducer work.  A real
>> patch in this direction would of course look very different.
>
> Another quick and dirty patch to make this specific example work ...

Thanks.

> diff --git a/guix/git.scm b/guix/git.scm
[...]
>  (define* (update-cached-checkout url
>                                   #:key
> -                                 (ref '(branch . "master"))
> +                                 (ref '(branch . "HEAD"))
>                                   recursive?
>                                   (check-out? #t)
>                                   starting-commit
> @@ -349,7 +313,9 @@ it unchanged."
>        (('branch . branch)
>         `(branch . ,(if (string-prefix? "origin/" branch)
>                         branch
> -                       (string-append "origin/" branch))))
> +                       (if (string=? "HEAD" branch)
> +                           branch
> +                           (string-append "origin/" branch)))))
>        (_ ref)))

I think using HEAD, rather than refs/remotes/origin/HEAD, will be
problematic when the repository is already present in the cache.  If I'm
reading guix/git.scm correctly, a fetch is done in that case.
refs/remotes/origin/HEAD will track any updates on the remote ref that
it points to, while HEAD will stay on the same commit that it landed on
at clone time.