Feature: Add git submodule support

[marvinhagemeister]

Just got assigned a project at work which includes submodules. Git blame doesn't seem to work on files which are not part of the root repository.

[WebReflection]

same here and it's not just about submodules, I'd say any folder that contains a .git one should have priority over the root folder (to be honest, even a way to temporarily change git blame info at runtime would be ace)

Thanks!

[Sertion]

This should work in 1.10.0.