Add help for --head.

gclient.py

 #!/usr/bin/python
 #
 # Copyright 2008 Google Inc.  All Rights Reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #      http://www.apache.org/licenses/LICENSE-2.0
 #
@@ skipping 111 matching lines @@
 This a synonym for 'gclient %(alias)s'
 
 usage: gclient %(cmd)s [options] [--] [svn update options/args]
 
 Valid options:
   --force             : force update even for unchanged modules
   --revision REV      : update/checkout all solutions with specified revision
   --revision SOLUTION@REV : update given solution to specified revision
   --deps PLATFORM(S)  : sync deps for the given platform(s), or 'all'
   --verbose           : output additional diagnostics
+  --head              : update to latest revision, instead of last good revision
 
 Examples:
   gclient %(cmd)s
       update files from SVN according to current configuration,
       *for modules which have changed since last update or sync*
   gclient %(cmd)s --force
       update files from SVN according to current configuration, for
       all modules (useful for recovering files deleted from local copy)
 """)
 
@@ skipping 1599 matching lines @@
 
 if "__main__" == __name__:
   try:
     result = Main(sys.argv)
   except Error, e:
     print >> sys.stderr, "Error: %s" % str(e)
     result = 1
   sys.exit(result)
 
 # vim: ts=2:sw=2:tw=80:et: