message: refactor: keep single source of truth
diff: @@ -86,7 +86,7 @@ function initProps (vm: Component, propsOptions: Object) {
  )
  }
  defineReactive(props, key, value, () => {
  - if (vm.$parent && !isUpdatingChildComponent) {
  + if (!isRoot && !isUpdatingChildComponent) {
  warn(
  `Avoid mutating a prop directly since the value will be ` +
  `overwritten whenever the parent component re-renders. ` +
  