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

recipe_engine/doc.py

 #!/usr/bin/env python
 # Copyright 2013 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.
 
 from __future__ import print_function, absolute_import
 
 import ast
 import inspect
 import json
@@ skipping 453 matching lines @@
     'List all known modules reachable from the current package, with their '
     'documentation.'
   )
   doc_p = parser.add_parser(
     'doc', help=helpstr, description=helpstr)
   doc_p.add_argument('recipe', nargs='?',
                      help='Restrict documentation to this recipe')
   doc_p.add_argument('--kind', default='jsonpb', choices=doc_kinds,
                      help='Output this kind of documentation')
 
-  doc_p.set_defaults(command='doc', func=main)
+  doc_p.set_defaults(func=main)
 
 
 def main(package_deps, args):
   universe = loader.RecipeUniverse(package_deps, args.package)
   universe_view = loader.UniverseView(universe, package_deps.root_package)
 
   logging.basicConfig()
 
   spec = universe_view.package.repo_spec.spec_pb()
   base_dir = universe_view.package.repo_root
@@ skipping 12 matching lines @@
   if args.kind == 'jsonpb':
     sys.stdout.write(jsonpb.MessageToJson(
       node, including_default_value_fields=True,
       preserving_proto_field_name=True))
   elif args.kind == 'binarypb':
     sys.stdout.write(node.SerializeToString())
   elif args.kind == 'textpb':
     sys.stdout.write(textpb.MessageToString(node))
   else:
     raise NotImplementedError('--kind=%s' % args.kind)