Added comment.

Author: kmvanbrunt

cmd2/pt_utils.py

@@ -176,6 +176,7 @@ def add_command(self, string: str) -> None:
 
         Ensures consecutive duplicates are not stored.
         """
+        # self._loaded_strings is sorted newest to oldest, so we compare to the first element.
         if string and (not self._loaded_strings or self._loaded_strings[0] != string):
             super().append_string(string)