def override(config, option, escape=false, &blk)
      # override if given on the command line
      if opt = input[option]
        opt = CFMicro.escape_path(opt) if escape
        config[option] = opt
      end
      config[option] = yield unless config[option]
    end
def override(config, option, escape=false, &blk)
      # override if given on the command line
      if opt = input[option]
        opt = CFMicro.escape_path(opt) if escape
        config[option] = opt
      end
      config[option] = yield unless config[option]
    end
override with command line arguments and yield the block in case the option isn't set