Hello,

Here's a patch that add support for ssh authenticated repositories in
"clone" and "remote-fetch" methods of Guile-Git.

At first, I used Guile-SSH in the tests to start an SSH server, but as
"make-server" call of Guile-SSH is really low level, this is not very
realistic. I just ended up with a half-broken ssh server, poorly
implemented, after (too many hours) spent reading ssh dumps.

So the strategy is to spawn an openssh server for the tests. It seems to
work alright, using key based or ssh-agent authentication.

WDYT?

Mathieu