* show commit-status if context is require status checks to pass.
  * disable merge if new commit-id has not `commit-status` ok on `Status-checkes`.
  * if some status includes required is not success, merge button is disabled.
  * if any required status is success, and some status not includes required, merge button is active, but button color is white.
  * if any required status is success, merge button is active, and button color is green.