Allow the git commit-log to be constrained by given paths

[Spiralis]

With this feature in place only git commits touching code within the given paths is considered a potential version source.

The "given paths" will in practical terms be the paths that a given project within the repo uses for it's files. The reason for allowing multiple paths, is that in C# a project may have other project references that also live in the same repo. A change in a dependent project should also count as a commit for the consuming project. To be seen in context of the changes suggested in #17.