code: def set_indexing(working_dir, flag):
      
      indexing_path = get_indexing_lockfile(working_dir)
      if flag:
          try:
              fd = open( indexing_path, "w+" )
              fd.close()
              return True
          except:
              return False
  
      else:
          try:
              os.unlink( indexing_path )
              return True
          except:
              return False
docs: Set a flag in the filesystem as to whether or not we're indexing.