Add script for appending entries to .gitignore.

TBR=kjellander

Review URL: https://webrtc-codereview.appspot.com/1629004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4193 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/build/extra_gitignore.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+# Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+""" Adds extra patterns to the root .gitignore file.
+
+Reads the contents of the filename given as the first argument and appends
+them to the root .gitignore file. The new entires are intended to be additional
+ignoring patterns, or negating patterns to override existing entries (man
+gitignore for more details).
+"""
+
+import os
+import sys
+
+MODIFY_STRING = '# The following added by %s\n'
+
+def main(argv):
+  if not argv[1]:
+    # Special case; do nothing.
+    return 0
+
+  modify_string = (MODIFY_STRING % argv[0])
+  gitignore_file = os.path.dirname(argv[0]) + '/../.gitignore'
+  lines = open(gitignore_file, 'r').readlines()
+  for i, line in enumerate(lines):
+    if line == modify_string:
+      lines = lines[:i]
+      break
+  lines.append(modify_string)
+
+  f = open(gitignore_file, 'w')
+  f.write(''.join(lines))
+  f.write(open(argv[1], 'r').read())
+  f.close()
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))