[recipes.py] Move fetch, lint and bundle parsers to separate modules.

recipe_engine/fetch.py

 # Copyright 2016 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.
 
 import calendar
 import httplib
 import json
 import logging
 import os
 import re
@@ skipping 574 matching lines @@
     spec = json_format.Parse(
       recipes_cfg_text, package_pb2.Package(), ignore_unknown_fields=True)
 
     return CommitMetadata(
       revision,
       rev_json.author_email,
       rev_json.commit_timestamp,
       rev_json.message_lines,
       spec,
       has_interesting_changes(spec, rev_json.changed_files))
+
+
+def add_subparser(parser):
+  fetch_p = parser.add_parser(
+    'fetch',
+    description='Fetch and update dependencies.')
+
+  def postprocess_func(parser, args):
+    if args.no_fetch:
+      parser.error('--no-fetch doesn\'t make sense with fetch command')
+
+  fetch_p.set_defaults(
+    command='fetch',
+    # fetch action is implied by recipes.py
+    func=(lambda package_deps, engine_flags: 0),
+    postprocess_func=postprocess_func,
+  )