tor-parallel-relay-conn/changes/ticket30979

  o Minor features (git hooks):
    - Our pre-commit git hook now checks for a special file
      before running practracker, so that practracker only runs on branches
      that are based on master. Since the pre-push hook calls the pre-commit
      hook, practracker will also only run before pushes of branches based
      on master.
      Closes ticket 30979.