docker_registry.lib.index.db: Support empty-query searches

Avoid building queries like:

  SELECT
    repository.id AS repository_id,
    repository.name AS repository_name,
    repository.description AS repository_description
  FROM repository
  WHERE repository.name LIKE %% OR repository.description LIKE %%

When folks don't specify a query term.

Reported-by: Don Laidlaw <don@donlaidlaw.ca>

Author: wking

docker_registry/lib/index/__init__.py

@@ -62,7 +62,7 @@ def _handle_repository_updated(
     def _handle_repository_deleted(self, sender, namespace, repository):
         pass
 
-    def results(self, search_term):
+    def results(self, search_term=None):
         """Return a list of results matching search_term
 
         The list elements should be dictionaries:

docker_registry/lib/index/db.py

@@ -114,13 +114,15 @@ def _handle_repository_deleted(self, sender, namespace, repository):
         session.commit()
         session.close()
 
-    def results(self, search_term):
+    def results(self, search_term=None):
         session = self._session()
-        like_term = '%%%s%%' % search_term
-        repositories = session.query(Repository).filter(
-            sqlalchemy.sql.or_(
-                Repository.name.like(like_term),
-                Repository.description.like(like_term)))
+        repositories = session.query(Repository)
+        if search_term:
+            like_term = '%%%s%%' % search_term
+            repositories = repositories.filter(
+                sqlalchemy.sql.or_(
+                    Repository.name.like(like_term),
+                    Repository.description.like(like_term)))
         return [
             {
                 'name': repo.name,