Basic labels support

Adds basic labels support to the registry code (V2), and the API. Note that this does not yet add any UI related support.

data/model/repository.py

@@ -10,7 +10,8 @@ from data.model import (DataModelException, tag, db_transaction, storage, permis
 from data.database import (Repository, Namespace, RepositoryTag, Star, Image, User,
                            Visibility, RepositoryPermission, RepositoryActionCount,
                            Role, RepositoryAuthorizedEmail, TagManifest, DerivedStorageForImage,
-                           get_epoch_timestamp, db_random_func)
+                           Label, TagManifestLabel, db_for_update, get_epoch_timestamp,
+                           db_random_func)
 
 
 logger = logging.getLogger(__name__)
@@ -50,11 +51,24 @@ def _purge_all_repository_tags(namespace_name, repository_name):
     raise DataModelException('Invalid repository \'%s/%s\'' %
                              (namespace_name, repository_name))
 
-  # Delete all manifests.
+  # Finds all the tags to delete.
   repo_tags = list(RepositoryTag.select().where(RepositoryTag.repository == repo.id))
   if not repo_tags:
     return
 
+  # Find all labels to delete.
+  labels = list(TagManifestLabel
+                .select(TagManifestLabel.label)
+                .where(TagManifestLabel.repository == repo))
+
+  # Delete all the mapping entries.
+  TagManifestLabel.delete().where(TagManifestLabel.repository == repo).execute()
+
+  # Delete all the matching labels.
+  if labels:
+    Label.delete().where(Label.id << [label.id for label in labels]).execute()
+
+  # Delete all the manifests.
   TagManifest.delete().where(TagManifest.tag << repo_tags).execute()
 
   # Delete all tags.