title: GitLab CI denies access to push using a deploy key with write access
body: <p>I added a deploy key with write access to my GitLab repository. My <code>.gitlab-ci.yml</code> file contains: </p>
  
  <pre><code>- git clone git@gitlab.domain:user/repo.git
  - git checkout master
  - git add myfile.pdf
  - git commit -m "Generated PDF file"
  - git push origin master
  </code></pre>
  
  <p>The deploy key works when cloning the repository.
  Pushing is not possible, even if the deploy key has write access.</p>
  
  <pre><code>remote: You are not allowed to upload code.
  fatal: unable to access 'https://gitlab-ci-token:xxxxxxxxxxxxxxxxxxxx@domain/user/repo.git/': The requested URL returned error: 403
  </code></pre>