[recipes.py] use argparse to set command automatically.

recipe_engine/lint_test.py

 #!/usr/bin/env python
 # Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Tests that recipes are on their best behavior.
 
 Checks that recipes only import modules from a whitelist.  Imports are
 generally not safe in recipes if they depend on the platform, since
 e.g. you can run a recipe simulation for a Windows recipe on Linux.
@@ skipping 54 matching lines @@
   # TODO(iannucci): merge this with the test command, doesn't need to be top
   # level.
   helpstr = 'Check recipes for stylistic and hygenic issues.'
   lint_p = parser.add_parser(
       'lint', help=helpstr, description=helpstr)
   lint_p.add_argument(
       '--whitelist', '-w', action='append', default=[],
       help='A regexp matching module names to add to the default whitelist. '
            'Use multiple times to add multiple patterns,')
 
-  lint_p.set_defaults(command='lint', func=main)
+  lint_p.set_defaults(func=main)
 
 
 def main(package_deps, args):
   from . import loader
 
   universe = loader.RecipeUniverse(package_deps, args.package)
   universe_view = loader.UniverseView(universe, package_deps.root_package)
 
   whitelist = map(re.compile, MODULES_WHITELIST + args.whitelist)
 
   errors = []
   for recipe_path, recipe_name in universe_view.loop_over_recipes():
     errors.extend(
         ImportsTest(recipe_path, recipe_name, whitelist, universe_view))
 
   if errors:
     raise TestFailure('\n'.join(map(str, errors)))