Add _catalog endpoint as specified by V2 API

Fixes #391

endpoints/v2/tag.py

@@ -1,28 +1,15 @@
 # XXX This code is not yet ready to be run in production, and should remain disabled until such
 # XXX time as this notice is removed.
 
-from flask import jsonify, request, url_for
+from flask import jsonify, url_for
 
-from app import get_app_url
 from endpoints.v2 import v2_bp, require_repo_read
 from endpoints.v2.errors import NameUnknown
+from endpoints.v2.v2util import add_pagination
 from auth.jwt_auth import process_jwt_auth
 from endpoints.decorators import anon_protect
 from data import model
 
-def _add_pagination(query, url):
-  limit = request.args.get('n', None)
-  page = request.args.get('page', 1)
-
-  if limit is None:
-    return None, query
-
-  url = get_app_url() + url
-  query = query.paginate(page, limit)
-  link = url + '?n=%s&last=%s; rel="next"' % (limit, page + 1)
-  return link, query
-
-
 @v2_bp.route('/<namespace>/<repo_name>/tags/list', methods=['GET'])
 @process_jwt_auth
 @require_repo_read
@@ -35,7 +22,7 @@ def list_all_tags(namespace, repo_name):
   query = model.tag.list_repository_tags(namespace, repo_name)
 
   url = url_for('v2.list_all_tags', namespace=namespace, repo_name=repo_name)
-  link, query = _add_pagination(query, url)
+  link, query = add_pagination(query, url)
 
   response = jsonify({
     'name': '{0}/{1}'.format(namespace, repo_name),