git: Renaming and refactoring

Renamed Git to Run so that it is invoked as git.Run
Runamed RunGitCommand to RunCommand.

Moved some functions around, added a few git command wrappers.

Story-Id: SF-42
Change-Id: 07c7fa1537
review post: Fix code review issues

Change a message to make it more descriptive.

Change-Id: dc98529d18
Story-Id: SF-15