Address review comments by @danielquinn

src/documents/models.py

@@ -484,11 +484,15 @@ class FileInfo:
         """
 
         filename = os.path.basename(path)
+
+        # Mutate filename in-place before parsing its components
+        # by applying at most one of the configured transformations.
         for (pattern, repl) in settings.FILENAME_PARSE_TRANSFORMS:
             (filename, count) = pattern.subn(repl, filename)
             if count:
                 break
 
+        # Parse filename components.
         for regex in cls.REGEXES.values():
             m = regex.match(filename)
             if m: