Allow empty git commit

[tombasche]

With some of our salt config we sometimes need to push an empty commit (with the commit message being the name of the service we need to redeploy).

It's also good if you need to trigger any other sort of commit hooks where the commit message is used for some purpose.

I tried as much as possible to just slimly insert this feature alongside the rest of the git stuff.

[msftclas]

All CLA requirements met.

[joaomoreno]

Thanks! 🍻