title: Add remote tag to a docker image
body: <p>On a private registry (myregistry.com), say I have an image tagged with 'v1.2.3'. I then push it by:</p>
  
  <p><code>docker push myregistry.com/myimage:v1.2.3</code></p>
  
  <p>If I want to associate another tag, say 'staging', and push that tag to my registry, I can:</p>
  
  <pre><code>docker tag myregistry.com/myimage:v1.2.3 myregistry.com/myimage:staging
  docker push myregistry.com/myimage:staging
  </code></pre>
  
  <p>Though this works, the second <code>docker push</code> still runs through each image, attempting to push it (albeit skipping upload). Is there a better way just to add a remote tag?</p>