Document native git options

[saitheexplorer]

I was attempting to make an empty commit with git commit --allow-empty, and after digging through the source, I was able to pass in {'allow-empty': true} to the commit function to get this to work.

the Repo#status docs make a vague reference to this capability, but it's not clear that this would work on any function.

Possible to include this in the docs?

[notatestuser]

Sure. Could you send a pull request?