new_contents: #!/usr/bin/env python
  
  import os
  import re
  import glob
  import shutil
  import datetime
  import sys
  import getopt
  import pipes
  import subprocess
  
  SOURCE_DIR = os.path.realpath(os.path.dirname(os.path.realpath(__file__)) + '/..')
  BUILD_SCRIPT = SOURCE_DIR + '/build-script.py'
  GYB_GEN_SOURCE_DIR = SOURCE_DIR + '/Sources/SwiftSyntax/gyb_generated/'
  
  def escapeCmdArg(arg):
      if '"' in arg or ' ' in arg:
          return '"%s"' % arg.replace('"', '\\"')
      else:
          return arg
  
  # Git Utils
  def git(git_command, cwd):
      '''Run a git command.'''
      command = ['git'] + git_command
      check_call(command, cwd=cwd, verbose=True)
  
  def git_tag(tag,src_path):
    '''Tag git repo'''
    git(['tag','-a',tag,'-m','Tag build ' + tag],src_path)
  
  def git_push_tag(tag,src_path):
    '''Push git tag'''
    git(['push', 'origin', tag], src_path)
  
  def git_clone(repo_url,src_path):
    '''Push git tag'''
    git(['clone', repo_url], src_path)
  
  def check_call(cmd, cwd=None, env=os.environ, verbose=False):
      if verbose:
          print(' '.join([escapeCmdArg(arg) for arg in cmd]))
      return subprocess.check_call(cmd, cwd=cwd, env=env, stderr=subprocess.STDOUT)
  
  def degyb():
      check_call([BUILD_SCRIPT, '--degyb-only'])
  
  def main(argv):
  	# Generate gyb files
  	degyb()
  	# Force commit gyb files
  	git(git_command=['add', '-f', GYB_GEN_SOURCE_DIR + '/*.swift'], cwd=SOURCE_DIR)
  	git(git_command=['commit', '-m', 'Auto-commit: add degybed files'], cwd=SOURCE_DIR)
  
  if __name__ == "__main__":
    main(sys.argv[1:])
  
subject: add a script to commit gyb-generated files.