Bug 1108399 - Handle help on mach sub-commands; r=ahal

--HG--
extra : rebase_source : b0a0ce3f5f6bf31ee3e0cd7d7cfd3be0fa9db598
extra : histedit_source : 2aee6a7bba61ce8074df1ed5edcd7fc2d27c5bf8

python/mach/mach/dispatcher.py

@@ -122,6 +122,21 @@ class CommandAction(argparse.Action):
 
         handler = self._mach_registrar.command_handlers.get(command)
 
+        # If there are sub-commands, parse the intent out immediately.
+        if handler.subcommand_handlers:
+            if not args:
+                self._handle_subcommand_main_help(parser, handler)
+                sys.exit(0)
+            elif len(args) == 1 and args[0] in ('help', '--help'):
+                self._handle_subcommand_main_help(parser, handler)
+                sys.exit(0)
+            # mach <command> help <subcommand>
+            elif len(args) == 2 and args[0] == 'help':
+                subcommand = args[1]
+                subhandler = handler.subcommand_handlers[subcommand]
+                self._handle_subcommand_help(parser, command, subcommand, subhandler)
+                sys.exit(0)
+
         # We create a new parser, populate it with the command's arguments,
         # then feed all remaining arguments to it, merging the results
         # with ourselves. This is essentially what argparse subparsers
@@ -267,6 +282,10 @@ class CommandAction(argparse.Action):
         if not handler:
             raise UnknownCommandError(command, 'query')
 
+        if handler.subcommand_handlers:
+            self._handle_subcommand_main_help(parser, handler)
+            return
+
         # This code is worth explaining. Because we are doing funky things with
         # argument registration to allow the same option in both global and
         # command arguments, we can't simply put all arguments on the same
@@ -316,6 +335,30 @@ class CommandAction(argparse.Action):
         print('')
         c_parser.print_help()
 
+    def _handle_subcommand_main_help(self, parser, handler):
+        parser.usage = '%(prog)s [global arguments] ' + handler.name + \
+            ' subcommand [subcommand arguments]'
+        group = parser.add_argument_group('Sub Commands')
+
+        for subcommand, subhandler in sorted(handler.subcommand_handlers.iteritems()):
+            group.add_argument(subcommand, help=subhandler.description,
+                action='store_true')
+
+        parser.print_help()
+
+    def _handle_subcommand_help(self, parser, command, subcommand, handler):
+        parser.usage = '%(prog)s [global arguments] ' + command + \
+            ' ' + subcommand + ' [command arguments]'
+
+        c_parser = argparse.ArgumentParser(add_help=False,
+            formatter_class=CommandFormatter)
+        group = c_parser.add_argument_group('Sub Command Arguments')
+        self._populate_command_group(c_parser, handler, group)
+
+        parser.print_help()
+        print('')
+        c_parser.print_help()
+
 class NoUsageFormatter(argparse.HelpFormatter):
     def _format_usage(self, *args, **kwargs):
         return ""