RepoPick : Add support for git pull

Allow user to git pull patchsets and dependencies.

Change-Id: If5520b45fe79836eac628b3caf0526f11f8953d9
roomservice: Fix assumptions about the branch naming

We can't just split from the last slash anymore, since we're using
those to distinguish the stabilization branches

Change-Id: Ia175dd317f508e99b275b56e9c83bd4729a75ddb
Merge "RepoPick : Add support for git pull" into cm-10.2