Start on a basic registry_model interface and change a single module to use it. This will allow us to completely abstract out how we deal with registry-related tables and ensure that transitioning to the new OCI-like model will be easier to do.

data/model/tag.py

@@ -722,3 +722,30 @@ def change_tag_expiration(tag, expiration_date):
             .execute())
 
   return (tag.lifetime_end_ts, result > 0)
+
+
+def find_matching_tag(repo_id, tag_names):
+  """ Finds the most recently pushed alive tag in the repository with one of the given names,
+      if any.
+  """
+  try:
+    return (_tag_alive(RepositoryTag
+                       .select()
+                       .where(RepositoryTag.repository == repo_id,
+                              RepositoryTag.name << list(tag_names))
+                       .order_by(RepositoryTag.lifetime_start_ts.desc()))
+            .get())
+  except RepositoryTag.DoesNotExist:
+    return None
+
+
+def get_most_recent_tag(repo_id):
+  """ Returns the most recently pushed alive tag in the repository, or None if none. """
+  try:
+    return (_tag_alive(RepositoryTag
+                       .select()
+                       .where(RepositoryTag.repository == repo_id)
+                       .order_by(RepositoryTag.lifetime_start_ts.desc()))
+            .get())
+  except RepositoryTag.DoesNotExist:
+    return None