title: gcloud promote a version
body: <p>So, I've deployed a custom runtime to gcloud (with --no-promote), using:</p>
  
  <pre><code>gcloud preview app deploy --project $PROJECT_NAME --version ${VERSION} --no-promote --quiet app.yaml
  </code></pre>
  
  <p>I saw that it all works well, and now I want to route traffic to it.
  Using the UI, it is simple - just checking the version's checkbox, and clicking a button.</p>
  
  <p>However, from the CLI, it appears that I need specify the app.yaml again.
  Why is that? Everything was already deployed...</p>
  
  <p>Is there a way to route traffic to it (i.e., "promote" it), without having to specify app.yaml again? i.e., other means rather than:</p>
  
  <pre><code>gcloud preview app deploy --project $PROJECT_NAME --version ${VERSION} --promote --quiet app.yaml
  </code></pre>
  
  <p>Thanks for all your help.</p>
  
  <p>Cheers,</p>
  
  <p>Ohad</p>