如何根据不同的sbt命令设置SettingKey的值？

val mySettingKey = settingKey[String]("Description of mySettingKey")

onLoad := {
  val mode = sys.props.getOrElse("mode", "default")
  mode match {
    case "dev" => mySettingKey := "dev value"
    case "prod" => mySettingKey := "prod value"
    case _ => mySettingKey := "default value"
  }
  onLoad.value
}

commands += Command.command("setSettingKey") { state =>
  val mode = sys.props.getOrElse("mode", "default")
  mode match {
    case "dev" => Project.extract(state).append(Seq(mySettingKey := "dev value"), state)
    case "prod" => Project.extract(state).append(Seq(mySettingKey := "prod value"), state)
    case _ => Project.extract(state).append(Seq(mySettingKey := "default value"), state)
  }
}

sbt setSettingKey