Assumes master branch

[Mark Vander Stel]

profile-manager assumes that the master branch is the default and that it is the branch that is wanted.

This is really a two sided issue:

1. When cloning from a remote, git checks out the default branch. We need to check for updates against and update the default branch.
2. If the user specifies a specific branch, we need to checkout, check updates, and update against that specific branch.

The first part is simple to fix, but the second issue is slightly trickier. The real challenge is supporting both.