def invoke_task(task_string) # :nodoc:
      name, args = parse_task_string(task_string)
      t = self[name]
      t.invoke(*args)
    end
def invoke_task(task_string) # :nodoc:
      name, args = parse_task_string(task_string)
      t = self[name]
      t.invoke(*args)
    end
internal ----------------------------------------------------------------
 Invokes a task with arguments that are extracted from +task_string+