prow/plugins/size/size.go
func isPRChanged(pe github.PullRequestEvent) bool {
	switch pe.Action {
	case github.PullRequestActionOpened:
		return true
	case github.PullRequestActionReopened:
		return true
	case github.PullRequestActionSynchronize:
		return true
	case github.PullRequestActionEdited:
		return true
	default:
		return false
	}
}
func isPRChanged(pe github.PullRequestEvent) bool {
	switch pe.Action {
	case github.PullRequestActionOpened:
		return true
	case github.PullRequestActionReopened:
		return true
	case github.PullRequestActionSynchronize:
		return true
	case github.PullRequestActionEdited:
		return true
	default:
		return false
	}
}
// These are the only actions indicating the code diffs may have changed.