add the Command.gen_opts option group

Note that commands still have to add the option group to the parser
once they populate it with options (self.parser.add_option_group).

pip/basecommand.py

@@ -43,6 +43,9 @@ class Command(object):
         self.main_parser = main_parser
         self.parser = ConfigOptionParser(**parser_kw)
 
+        # Commands should add options to this option group
+        self.cmd_opts = optparse.OptionGroup(self.parser, 'Command Options')
+
         # Re-add all options and option groups.
         for group in main_parser.option_groups:
             self._copy_option_group(self.parser, group)

pip/commands/install.py

@@ -23,7 +23,7 @@ class InstallCommand(Command):
         super(InstallCommand, self).__init__(*args, **kw)
 
         pypi_opts = optparse.OptionGroup(self.parser, 'Package Index Options')
-        cmd_opts = optparse.OptionGroup(self.parser, 'Command Options')
+        cmd_opts = self.cmd_opts
 
         pypi_opts.add_option(
             '-f', '--find-links',