[cli/utils] Reintroduce custom parser for hidden aliases

I don't want to break people's muscle memory, but I also don't want
to have the help output be messier than it needs to be.

legendary/cli.py

@@ -23,6 +23,7 @@ from legendary.models.exceptions import InvalidCredentialsError
 from legendary.models.game import SaveGameStatus, VerifyResult, Game
 from legendary.utils.cli import get_boolean_choice, get_int_choice, sdl_prompt, strtobool
 from legendary.utils.crossover import *
+from legendary.utils.custom_parser import HiddenAliasSubparsersAction
 from legendary.utils.env import is_windows_mac_or_pyi
 from legendary.utils.eos import add_registry_entries, query_registry_entries, remove_registry_entries
 from legendary.utils.lfs import validate_files, clean_filename
@@ -2350,6 +2351,7 @@ class LegendaryCLI:
 
 def main():
     parser = argparse.ArgumentParser(description=f'Legendary v{__version__} - "{__codename__}"')
+    parser.register('action', 'parsers', HiddenAliasSubparsersAction)
 
     # general arguments
     parser.add_argument('-H', '--full-help', dest='full_help', action='store_true',

legendary/utils/custom_parser.py

@@ -0,0 +1,28 @@
+import argparse
+
+
+class HiddenAliasSubparsersAction(argparse._SubParsersAction):
+    def add_parser(self, name, **kwargs):
+        # set prog from the existing prefix
+        if kwargs.get('prog') is None:
+            kwargs['prog'] = '%s %s' % (self._prog_prefix, name)
+
+        aliases = kwargs.pop('aliases', ())
+        hide_aliases = kwargs.pop('hide_aliases', False)
+
+        # create a pseudo-action to hold the choice help
+        if 'help' in kwargs:
+            help = kwargs.pop('help')
+            _aliases = None if hide_aliases else aliases
+            choice_action = self._ChoicesPseudoAction(name, _aliases, help)
+            self._choices_actions.append(choice_action)
+
+        # create the parser and add it to the map
+        parser = self._parser_class(**kwargs)
+        self._name_parser_map[name] = parser
+
+        # make parser available under aliases also
+        for alias in aliases:
+            self._name_parser_map[alias] = parser
+
+        return parser