First few changes for the image diffs feature.

endpoints/api.py

@@ -360,6 +360,21 @@ def list_repository_images(namespace, repository):
   abort(403)
 
 
+@app.route('/api/repository/<path:repository>/image/<image_id>/changes',
+           methods=['GET'])
+@parse_repository_name
+def get_repository_changes(namespace, repository, image_id):
+  permission = ReadRepositoryPermission(namespace, repository)
+  if permission.can() or model.repository_is_public(namespace, repository):
+    return jsonify({
+      'added': [],
+      'changed': [],
+      'removed': []
+    })
+
+  abort(403)
+
+
 @app.route('/api/repository/<path:repository>/tag/<tag>/images',
            methods=['GET'])
 @parse_repository_name