docs: def discoverCurrentWorkingDevice(procMounts='/proc/self/mounts'):
      """
      Return a short string naming the device which backs the current working
      directory, ie C{/dev/hda1}.
      """
      possibilities = []
      cwd = os.getcwd()
      with file(procMounts, 'rb') as f:
          for L in f:
              parts = L.split()
              if cwd.startswith(parts[1]):
                  possibilities.append((len(parts[1]), parts[0]))
      possibilities.sort()
      try:
          return possibilities[-1][-1]
      except IndexError:
          return '<unknown>'