--print_bots arg to 'gcl try' for debugging PRESUBMIT.py changes.

trychange.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 """Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn repository or by directly connecting
 to the server by HTTP.
 """
 
@@ skipping 521 matching lines @@
   group.add_option("--dry_run", action='store_true',
                    help="Don't send the try job. This implies --verbose, so "
                         "it will print the diff.")
   parser.add_option_group(group)
 
   group = optparse.OptionGroup(parser, "Try job options")
   group.add_option("-b", "--bot", action="append",
                     help="Only use specifics build slaves, ex: "
                          "'--bot win,layout_mac'; see the try "
                          "server waterfall for the slave's name")
+  group.add_option("-B", "--print_bots", action="store_true",
+                    help="Print bots we would use (e.g. from PRESUBMIT.py)"
+                         " and exit.  Do not send patch.  Like --dry_run"
+                         " but less verbose.")
   group.add_option("-r", "--revision",
                     help="Revision to use for the try job; default: the "
                          "revision will be determined by the try server; see "
                          "its waterfall for more info")
   group.add_option("-c", "--clobber", action="store_true",
                     help="Force a clobber before building; e.g. don't do an "
                          "incremental build")
   # TODO(maruel): help="Select a specific configuration, usually 'debug' or "
   #                    "'release'"
   group.add_option("--target", help=optparse.SUPPRESS_HELP)
@@ skipping 229 matching lines @@
             checkouts[0].checkout_root,
             root_presubmit,
             options.project,
             False,
             sys.stdout)
       except ImportError:
         pass
       # If no bot is specified, either the default pool will be selected or the
       # try server will refuse the job. Either case we don't need to interfere.
 
+    if options.print_bots:
+      print 'Bots which would be used:'
+      for bot in options.bot:
+        print '  %s' % bot
+      return 0
+
     # Send the patch.
     if options.send_patch:
       # If forced.
       options.send_patch(options)
       PrintSuccess(options)
       return 0
     try:
       if can_http:
         _SendChangeHTTP(options)
         PrintSuccess(options)
@@ skipping 11 matching lines @@
     return 1
   except (gclient_utils.Error, subprocess2.CalledProcessError), e:
     print >> sys.stderr, e
     return 1
   return 0
 
 
 if __name__ == "__main__":
   fix_encoding.fix_encoding()
   sys.exit(TryChange(None, None, False))