title: GitLab-CI: run job only when a branch is delete
body: <p>In gitlab runner, I want to run job when the branch is deleted.</p>
  <p>(.yml example)</p>
  <pre><code>creat job:
    stage: delete
    script:
      - echo 'branch delete'
    only:
     - ????
  </code></pre>
  <pre><code>create:
    stage: delete
    script:
      - echo 'branch delete'
    rules:
      - if: '????'
  </code></pre>