title: ERROR: (gcloud.preview) Invalid choice: 'docker'. Did you mean 'dm-v2'?
body: <p>Somehow I was able to push my docker image to Google Container Registry with command:</p>
  
  <pre><code>    $ gcloud preview docker push gcr.io/&lt;my-project-xxx&gt;/&lt;my-image-yyy&gt;
  </code></pre>
  
  <p>I ran the commands yesterday and copied them to my notes, but today pasting them to terminal in the same order I get the error:</p>
  
  <p><strong>ERROR: (gcloud.preview) Invalid choice: 'docker'. Did you mean 'dm-v2'?</strong></p>
  
  <p>Why is that? where did teh "gcloud preview docker" command are then?</p>