Allow tags to be marked as hidden. Create a hidden tag on every image during a push to prevent them from getting GCed.

endpoints/registry.py

@@ -467,6 +467,10 @@ def put_image_json(namespace, repository, image_id):
     repo_image = model.find_create_or_link_image(image_id, repo, username, {},
                                                  store.preferred_locations[0])
 
+  # Create a temporary tag to prevent this image from getting garbage collected while the push
+  # is in progress.
+  model.create_temporary_hidden_tag(repo, repo_image, app.config['PUSH_TEMP_TAG_EXPIRATION_S'])
+
   uuid = repo_image.storage.uuid
 
   if image_id != data['id']: