Use argument groups for Android and desktop-only arguments.

mojo/devtools/common/devtoolslib/shell_arguments.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Functions that configure the shell before it is run manipulating its argument
 list.
 """
 
 import os.path
 import sys
@@ skipping 170 matching lines @@
   else:
     arguments.append(key + value)
 
   return arguments
 
 
 def add_shell_arguments(parser):
   """Adds argparse arguments allowing to configure shell abstraction using
   configure_shell() below.
   """
-  # Arguments indicating paths to binaries and tools.
-  parser.add_argument('--adb-path', help='Path of the adb binary.')
+  # Arguments configuring the shell run.
   parser.add_argument('--shell-path', help='Path of the Mojo shell binary.')
-
-  # Arguments configuring the shell run.
   parser.add_argument('--android', help='Run on Android',
                       action='store_true')
   parser.add_argument('--origin', help='Origin for mojo: URLs. This can be a '
                       'web url or a local directory path.')
   parser.add_argument('--map-url', action='append',
                       help='Define a mapping for a url in the format '
                       '<url>=<url-or-local-file-path>')
   parser.add_argument('--map-origin', action='append',
                       help='Define a mapping for a url origin in the format '
                       '<origin>=<url-or-local-file-path>')
-
-  # Android-only arguments.
-  parser.add_argument('--target-device',
-                      help='(android-only) Device to run on.')
-  parser.add_argument('--logcat-tags',
-                      help='(android-only) Comma-separated list of additional '
-                      'logcat tags to display on the console.')
-
-  # Desktop-only arguments.
-  parser.add_argument('--use-osmesa', action='store_true',
-                      help='(linux-only) Configure the native viewport service '
-                      'for off-screen rendering.')
-
-  # Other configuration.
   parser.add_argument('-v', '--verbose', action="store_true",
                       help="Increase output verbosity")
 
+  android_group = parser.add_argument_group('Android-only',
+      'These arguments apply only when --android is passed.')
+  android_group.add_argument('--adb-path', help='Path of the adb binary.')
+  android_group.add_argument('--target-device', help='Device to run on.')
+  android_group.add_argument('--logcat-tags', help='Comma-separated list of '
+                             'additional logcat tags to display.')
+
+  desktop_group = parser.add_argument_group('Desktop-only',
+      'These arguments apply only when running on desktop.')
+  desktop_group.add_argument('--use-osmesa', action='store_true',
+                             help='Configure the native viewport service '
+                             'for off-screen rendering.')
+
 
 class ShellConfigurationException(Exception):
   """Represents an error preventing creating a functional shell abstraction."""
   pass
 
 
 def configure_shell(config_args, shell_args):
   """
   Produces a shell abstraction configured using the parsed arguments defined in
   add_shell_arguments().
@@ skipping 34 matching lines @@
                                config_args.map_origin)
 
   if config_args.origin:
     if _is_web_url(config_args.origin):
       shell_args.append('--origin=' + config_args.origin)
     else:
       shell_args.extend(configure_local_origin(shell, config_args.origin,
                                              fixed_port=True))
 
   return shell, shell_args