Add a note warning the users that presubmit hooks will be run.

presubmit_support.py

 #!/usr/bin/python
 # Copyright (c) 2006-2009 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.
 
 """Enables directory-specific presubmit checks to run at upload and/or commit.
 """
 
 __version__ = '1.3.5'
 
@@ skipping 927 matching lines @@
     default_presubmit: A default presubmit script to execute in any case.
     may_prompt: Enable (y/n) questions on warning or error.
 
   Warning:
     If may_prompt is true, output_stream SHOULD be sys.stdout and input_stream
     SHOULD be sys.stdin.
 
   Return:
     True if execution can continue, False if not.
   """
+  print "Running presubmit hooks..."
   start_time = time.time()
   presubmit_files = ListRelevantPresubmitFiles(change.AbsoluteLocalPaths(True),
                                                change.RepositoryRoot())
   if not presubmit_files and verbose:
     output_stream.write("Warning, no presubmit.py found.\n")
   results = []
   executer = PresubmitExecuter(change, committing)
   if default_presubmit:
     if verbose:
       output_stream.write("Running default presubmit script.\n")
@@ skipping 129 matching lines @@
                                options.commit,
                                options.verbose,
                                sys.stdout,
                                sys.stdin,
                                options.default_presubmit,
                                options.may_prompt)
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))