Make "git cl format" format GN files.

git_cl.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.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
 from distutils.version import LooseVersion
@@ skipping 3516 matching lines @@
   return diff_cmd
 
 def MatchingFileType(file_name, extensions):
   """Returns true if the file name ends with one of the given extensions."""
   return bool([ext for ext in extensions if file_name.lower().endswith(ext)])
 
 @subcommand.usage('[files or directories to diff]')
 def CMDformat(parser, args):
   """Runs auto-formatting tools (clang-format etc.) on the diff."""
   CLANG_EXTS = ['.cc', '.cpp', '.h', '.mm', '.proto', '.java']
+  GN_EXTS = ['.gn', '.gni']
   parser.add_option('--full', action='store_true',
                     help='Reformat the full content of all touched files')
   parser.add_option('--dry-run', action='store_true',
                     help='Don\'t modify any file on disk.')
   parser.add_option('--python', action='store_true',
                     help='Format python code with yapf (experimental).')
   parser.add_option('--diff', action='store_true',
                     help='Print diff to stdout rather than modifying files.')
   opts, args = parser.parse_args(args)
 
@@ skipping 20 matching lines @@
 
   changed_files_cmd = BuildGitDiffCmd('--name-only', upstream_commit, args)
   diff_output = RunGit(changed_files_cmd)
   diff_files = diff_output.splitlines()
   # Filter out files deleted by this CL
   diff_files = [x for x in diff_files if os.path.isfile(x)]
 
   clang_diff_files = [x for x in diff_files if MatchingFileType(x, CLANG_EXTS)]
   python_diff_files = [x for x in diff_files if MatchingFileType(x, ['.py'])]
   dart_diff_files = [x for x in diff_files if MatchingFileType(x, ['.dart'])]
+  gn_diff_files = [x for x in diff_files if MatchingFileType(x, GN_EXTS)]
 
   top_dir = os.path.normpath(
       RunGit(["rev-parse", "--show-toplevel"]).rstrip('\n'))
 
   # Locate the clang-format binary in the checkout
   try:
     clang_format_tool = clang_format.FindClangFormatToolInChromiumTree()
   except clang_format.NotFoundError, e:
     DieWithError(e)
 
@@ skipping 61 matching lines @@
       command.extend(dart_diff_files)
 
       stdout = RunCommand(command, cwd=top_dir, env=env)
       if opts.dry_run and stdout:
         return_value = 2
     except dart_format.NotFoundError as e:
       print ('Warning: Unable to check Dart code formatting. Dart SDK not ' +
              'found in this checkout. Files in other languages are still ' +
              'formatted.')
 
+  # Format GN build files. Always run on full build files for canonical form.
+  if gn_diff_files:
+    cmd = ['gn', 'format']
+    if not opts.dry_run and not opts.diff:
+      cmd.append('--in-place')
+    for gn_diff_file in gn_diff_files:
+      stdout = RunCommand(cmd + [gn_diff_file], cwd=top_dir)
+      if opts.diff:
+        sys.stdout.write(stdout)
+
   return return_value
 
 
 @subcommand.usage('<codereview url or issue id>')
 def CMDcheckout(parser, args):
   """Checks out a branch associated with a given Rietveld issue."""
   _, args = parser.parse_args(args)
 
   if len(args) != 1:
     parser.print_help()
@@ skipping 86 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   colorama.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)