Added init, submodule add and fixed an issue with parsing the commit data

Hey @steveukx, looks like a good package here.  I have a project that uses a much more janky implementation.  I would like to switch over to this package, but I need a few more features.  If it is good with you, I will fork and upstream the features.

The commands I need are:
- `git init`
- `git submodule [add, init, update]`
- `git ls-remote --tags`

Do you have contributor guidelines?  Does this all sound good?