Ghetto implementation of git features.

Implement a the subset of git commands I need right now. This code
is kind of ghetto but it works.
Add base path trimming to Review

The tools will be running in a repo path, this is not the same
as the repo root, which is what comments need to be against.

Normalize paths in the review to match those in the repo.
Update tasks and add in place to add problem filtering.