bug#38320: Cuirass: Allow to use authenticated Git repositories as inputs

[Mathieu Othacehe <m.othacehe@gmail.com>]

Hello Clément,

> I think there are small modifications to do to (guix git) and (git
> clone).

I did integrate a part of libgit2 ssh authentification mechanism in
Guile-Git in 2017. You can find it in (git fetch) module.

It is currently broken, because of a regression. See
https://lists.gnu.org/archive/html/guix-devel/2019-11/msg00415.html.

What would be missing to have support for authenticated Git repositories
as Cuirass inputs is:

* Fix the regression mentionned above.

* Add support for a fetch-options argument in clone method of (git clone).

* In (guix git), "latest-repository-commit" method would take parameters
to setup ssh authentication (such as ssh private key path at least) and
pass them to "fetch" and "clone" methods of Guile-Git.

* Finally in Cuirass, the ssh authentication parameters could be
specified in the specification file (maybe for each input?) and passed
to "latest-repository-commit" method accordingly.

So there's still some work to do :)

Mathieu