Adding TODO about a helpful notice about legacy config.

borgmatic/commands/borgmatic.py

@@ -41,6 +41,9 @@ def parse_arguments(*arguments):
 
 def main():
     try:
+        # TODO: Detect whether only legacy config is present. If so, inform the user about how to
+        # upgrade, then exet.
+
         args = parse_arguments(*sys.argv[1:])
         config = parse_configuration(args.config_filename, schema_filename())
         repository = config.location['repository']