Make fetch help display all known recipes.

fetch.py

 #!/usr/bin/env python
 # Copyright (c) 2013 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.
 
 """
 Tool to perform checkouts in one easy command line!
 
 Usage:
   fetch <recipe> [--property=value [--property2=value2 ...]]
 
 This script is a wrapper around various version control and repository
 checkout commands. It requires a |recipe| name, fetches data from that
 recipe in depot_tools/recipes, and then performs all necessary inits,
 checkouts, pulls, fetches, etc.
 
 Optional arguments may be passed on the command line in key-value pairs.
 These parameters will be passed through to the recipe's main method.
 """
 
 import json
 import optparse
 import os
+import pipes
 import subprocess
 import sys
-import pipes
+import textwrap
 
 from distutils import spawn
 
 
 SCRIPT_PATH = os.path.dirname(os.path.abspath(__file__))
 
 #################################################
 # Checkout class definitions.
 #################################################
 class Checkout(object):
@@ skipping 153 matching lines @@
 
 
 #################################################
 # Utility function and file entry point.
 #################################################
 def usage(msg=None):
   """Print help and exit."""
   if msg:
     print 'Error:', msg
 
-  print (
-"""
-usage: %s [options] <recipe> [--property=value [--property2=value2 ...]]
+  print textwrap.dedent("""\
+    usage: %s [options] <recipe> [--property=value [--property2=value2 ...]]
 
-This script can be used to download the Chromium sources. See
-http://www.chromium.org/developers/how-tos/get-the-code
-for full usage instructions.
+    This script can be used to download the Chromium sources. See
+    http://www.chromium.org/developers/how-tos/get-the-code
+    for full usage instructions.
 
-Valid options:
-   -h, --help, help   Print this message.
-   --nohooks          Don't run hooks after checkout.
-   -n, --dry-run      Don't run commands, only print them.
-   --no-history       Perform shallow clones, don't fetch the full git history.
-""" % os.path.basename(sys.argv[0]))
+    Valid options:
+       -h, --help, help   Print this message.
+       --nohooks          Don't run hooks after checkout.
+       -n, --dry-run      Don't run commands, only print them.
+       --no-history       Perform shallow clones, don't fetch the full git history.
+
+    Valid fetch recipes:""") % os.path.basename(sys.argv[0])
+  for fname in os.listdir(os.path.join(SCRIPT_PATH, 'recipes')):
+    if fname.endswith('.py'):
+      print '  ' + fname[:-3]
+
   sys.exit(bool(msg))
 
 
 def handle_args(argv):
   """Gets the recipe name from the command line arguments."""
   if len(argv) <= 1:
     usage('Must specify a recipe.')
   if argv[1] in ('-h', '--help', 'help'):
     usage()
 
@@ skipping 79 matching lines @@
 
 
 def main():
   options, recipe, props = handle_args(sys.argv)
   spec, root = run_recipe_fetch(recipe, props)
   return run(options, spec, root)
 
 
 if __name__ == '__main__':
   sys.exit(main())