Fix support for pulling manifest lists via Docker V1 protocol where applicable

data/registry_model/registry_pre_oci_model.py

@@ -32,6 +32,13 @@ class PreOCIModel(SharedModel, RegistryDataInterface):
         manifests. """
     return False
 
+  def get_legacy_tags_map(self, repository_ref, storage):
+    """ Returns a map from tag name to its legacy image, for all tags with legacy images in
+        the repository.
+    """
+    tags = self.list_repository_tags(repository_ref, include_legacy_images=True)
+    return {tag.name: tag.legacy_image.docker_image_id for tag in tags}
+
   def find_matching_tag(self, repository_ref, tag_names):
     """ Finds an alive tag in the repository matching one of the given tag names and returns it
         or None if none.