fix(argparse_completer): suppress completion hint for subcommands

Subcommands completion hint (often a list of subcommands) was being displayed above the prompt, which is redundant when prompt-toolkit displays the subcommands in the completion menu. This change suppresses the hint for _SubParsersAction, allowing the completion menu to be the primary guide for subcommands.

Author: tleonhardt

cmd2/argparse_completer.py

@@ -460,8 +460,8 @@ def update_mutex_groups(arg_action: argparse.Action) -> None:
 
             # If we have results, then return them
             if completion_results:
-                # Don't overwrite an existing hint
-                if not self._cmd2_app.completion_hint:
+                # Don't overwrite an existing hint or show a hint for subcommands
+                if not self._cmd2_app.completion_hint and not isinstance(pos_arg_state.action, argparse._SubParsersAction):
                     self._cmd2_app.completion_hint = _build_hint(self._parser, pos_arg_state.action)
                 return completion_results