Add function in data interface for mounting blobs into other repositories

data/registry_model/registry_pre_oci_model.py

@@ -690,5 +690,22 @@ class PreOCIModel(RegistryDataInterface):
     return Blob.for_image_storage(blob_record,
                                   storage_path=model.storage.get_layer_path(blob_record))
 
+  def mount_blob_into_repository(self, blob, target_repository_ref, expiration_sec):
+    """
+    Mounts the blob from another repository into the specified target repository, and adds an
+    expiration before that blob is automatically GCed. This function is useful during push
+    operations if an existing blob from another repositroy is being pushed. Returns False if
+    the mounting fails.
+    """
+    repo = model.repository.lookup_repository(target_repository_ref._db_id)
+    if repo is None:
+      return False
+
+    namespace_name = repo.namespace_user.username
+    repo_name = repo.name
+
+    storage = model.blob.temp_link_blob(namespace_name, repo_name, blob.digest,
+                                        expiration_sec)
+    return bool(storage)
 
 pre_oci_model = PreOCIModel()