commands: Add initial --help argument support.

qutebrowser/commands/argparser.py

@@ -22,10 +22,15 @@
 
 import argparse
 
+from PyQt5.QtCore import QCoreApplication, QUrl
+
 from qutebrowser.commands import cmdexc
 from qutebrowser.utils import utils
 
 
+SUPPRESS = argparse.SUPPRESS
+
+
 class ArgumentParserError(Exception):
 
     """Exception raised when the ArgumentParser signals an error."""
@@ -40,11 +45,20 @@ class ArgumentParserExit(Exception):
         super().__init__(msg)
 
 
+class HelpAction(argparse.Action):
+
+    def __call__(self, parser, _namespace, _values, _option_string=None):
+        QCoreApplication.instance().mainwindow.tabs.tabopen(
+            QUrl('qute:help/commands.html#{}'.format(parser.name)))
+        parser.exit()
+
+
 class ArgumentParser(argparse.ArgumentParser):
 
     """Subclass ArgumentParser to be more suitable for runtime parsing."""
 
-    def __init__(self):
+    def __init__(self, name):
+        self.name = name
         super().__init__(add_help=False)
 
     def exit(self, status=0, msg=None):

qutebrowser/commands/cmdutils.py

@@ -167,6 +167,9 @@ class register:  # pylint: disable=invalid-name
             if name in cmd_dict:
                 raise ValueError("{} is already registered!".format(name))
         self.parser = argparser.ArgumentParser(names[0])
+        self.parser.add_argument('-h', '--help', action=argparser.HelpAction,
+                                default=argparser.SUPPRESS, nargs=0,
+                                help="Show this help message.")
         has_count, desc, type_conv = self._inspect_func()
         cmd = command.Command(
             name=names[0], split=self.split, hide=self.hide, count=has_count,