Allow to inject extra vars to environment

Signed-off-by: Michal Čihař <michal@cihar.com>
Use own SSH wrapper for Git

Issue #597

Signed-off-by: Michal Čihař <michal@cihar.com>
Correct handling of private and public SSH keys

Signed-off-by: Michal Čihař <michal@cihar.com>
Configure SSH wrapper for Mercurial

Issue #597

Signed-off-by: Michal Čihař <michal@cihar.com>