Checkout other Git implementations

[rhuss]

Currently we are using nodegit which is an inherently asynchronous JavaScript library. It is a bit tedious to use, documentation is also not that perfect. So maybe there is a better alternative ?

Also, since nodgit is async it is hard to include into the otherwise 'classical' script which use synchronous function calls (and their return values).

Alternatively, change the script to a use promises everywhere.