diff --git a/contrib/devtools/clang-format-diff.py b/contrib/devtools/clang-format-diff.py
new file mode 100755
index 000000000..9e02bb093
--- /dev/null
+++ b/contrib/devtools/clang-format-diff.py
@@ -0,0 +1,124 @@
+#!/usr/bin/env python
+#
+#===- clang-format-diff.py - ClangFormat Diff Reformatter ----*- python -*--===#
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+#===------------------------------------------------------------------------===#
+
+r"""
+ClangFormat Diff Reformatter
+============================
+
+This script reads input from a unified diff and reformats all the changed
+lines. This is useful to reformat all the lines touched by a specific patch.
+Example usage for git/svn users:
+
+  git diff -U0 HEAD^ | clang-format-diff.py -p1 -i
+  svn diff --diff-cmd=diff -x-U0 | clang-format-diff.py -i
+
+"""
+
+import argparse
+import difflib
+import re
+import string
+import subprocess
+import StringIO
+import sys
+
+
+# Change this to the full path if clang-format is not on the path.
+binary = 'clang-format'
+
+
+def main():
+  parser = argparse.ArgumentParser(description=
+                                   'Reformat changed lines in diff. Without -i '
+                                   'option just output the diff that would be '
+                                   'introduced.')
+  parser.add_argument('-i', action='store_true', default=False,
+                      help='apply edits to files instead of displaying a diff')
+  parser.add_argument('-p', metavar='NUM', default=0,
+                      help='strip the smallest prefix containing P slashes')
+  parser.add_argument('-regex', metavar='PATTERN', default=None,
+                      help='custom pattern selecting file paths to reformat '
+                      '(case sensitive, overrides -iregex)')
+  parser.add_argument('-iregex', metavar='PATTERN', default=
+                      r'.*\.(cpp|cc|c\+\+|cxx|c|cl|h|hpp|m|mm|inc|js|ts|proto'
+                      r'|protodevel|java)',
+                      help='custom pattern selecting file paths to reformat '
+                      '(case insensitive, overridden by -regex)')
+  parser.add_argument('-sort-includes', action='store_true', default=False,
+                      help='let clang-format sort include blocks')
+  parser.add_argument('-v', '--verbose', action='store_true',
+                      help='be more verbose, ineffective without -i')
+  parser.add_argument(
+      '-style',
+      help=
+      'formatting style to apply (LLVM, Google, Chromium, Mozilla, WebKit)')
+  args = parser.parse_args()
+
+  # Extract changed lines for each file.
+  filename = None
+  lines_by_file = {}
+  for line in sys.stdin:
+    match = re.search('^\+\+\+\ (.*?/){%s}(\S*)' % args.p, line)
+    if match:
+      filename = match.group(2)
+    if filename == None:
+      continue
+
+    if args.regex is not None:
+      if not re.match('^%s$' % args.regex, filename):
+        continue
+    else:
+      if not re.match('^%s$' % args.iregex, filename, re.IGNORECASE):
+        continue
+
+    match = re.search('^@@.*\+(\d+)(,(\d+))?', line)
+    if match:
+      start_line = int(match.group(1))
+      line_count = 1
+      if match.group(3):
+        line_count = int(match.group(3))
+      if line_count == 0:
+        continue
+      end_line = start_line + line_count - 1;
+      lines_by_file.setdefault(filename, []).extend(
+          ['-lines', str(start_line) + ':' + str(end_line)])
+
+  # Reformat files containing changes in place.
+  for filename, lines in lines_by_file.iteritems():
+    if args.i and args.verbose:
+      print 'Formatting', filename
+    command = [binary, filename]
+    if args.i:
+      command.append('-i')
+    if args.sort_includes:
+      command.append('-sort-includes')
+    command.extend(lines)
+    if args.style:
+      command.extend(['-style', args.style])
+    p = subprocess.Popen(command, stdout=subprocess.PIPE,
+                         stderr=None, stdin=subprocess.PIPE)
+    stdout, stderr = p.communicate()
+    if p.returncode != 0:
+      sys.exit(p.returncode);
+
+    if not args.i:
+      with open(filename) as f:
+        code = f.readlines()
+      formatted_code = StringIO.StringIO(stdout).readlines()
+      diff = difflib.unified_diff(code, formatted_code,
+                                  filename, filename,
+                                  '(before formatting)', '(after formatting)')
+      diff_string = string.join(diff, '')
+      if len(diff_string) > 0:
+        sys.stdout.write(diff_string)
+
+if __name__ == '__main__':
+  main()