Refactor the util directory to use subpackages.

util/registry/aufs.py

@@ -0,0 +1,31 @@
+import os
+
+AUFS_METADATA = u'.wh..wh.'
+AUFS_WHITEOUT = u'.wh.'
+AUFS_WHITEOUT_PREFIX_LENGTH = len(AUFS_WHITEOUT)
+
+def is_aufs_metadata(absolute):
+  """ Returns whether the given absolute references an AUFS metadata file. """
+  filename = os.path.basename(absolute)
+  return filename.startswith(AUFS_METADATA) or absolute.startswith(AUFS_METADATA)
+
+def get_deleted_filename(absolute):
+  """ Returns the name of the deleted file referenced by the AUFS whiteout file at
+      the given path or None if the file path does not reference a whiteout file.
+  """
+  filename = os.path.basename(absolute)
+  if not filename.startswith(AUFS_WHITEOUT):
+    return None
+
+  return filename[AUFS_WHITEOUT_PREFIX_LENGTH:]
+
+def get_deleted_prefix(absolute):
+  """ Returns the path prefix of the deleted file referenced by the AUFS whiteout file at
+     the given path or None if the file path does not reference a whiteout file.
+  """
+  deleted_filename = get_deleted_filename(absolute)
+  if deleted_filename is None:
+    return None
+
+  dirname = os.path.dirname(absolute)
+  return os.path.join('/', dirname, deleted_filename)[1:]