Lets you run sort-headers.py on all files changed since some git branch.

tools/git/for-all-touched-files.py

Index: tools/git/for-all-touched-files.py
diff --git a/tools/git/for-all-touched-files.py b/tools/git/for-all-touched-files.py
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index 0000000000000000000000000000000000000000..d776743bec9ac5a773339d06267d39974032d605
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+++ b/tools/git/for-all-touched-files.py
@@ -0,0 +1,114 @@
+#!/usr/bin/python
+# Copyright (c) 2011 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.
+
+"""
+  Invokes the specified (quoted) command for all files modified
+  between the current git branch and the specified branch or commit.
+
+  The special token [[FILENAME]] (or whatever you choose using the -t
+  flag) is replaced with each of the filenames of new or modified files.
+
+  Deleted files are not included.  Neither are untracked files.
+
+Synopsis:
+  %prog [-b BRANCH] [-d] [-x EXTENSIONS|-c] [-t TOKEN] QUOTED_COMMAND
+
+Examples:
+  %prog -x gyp,gypi "tools/format_xml.py [[FILENAME]]"
+  %prog -c "tools/sort-headers.py [[FILENAME]]"
+  %prog -t "~~BINGO~~" "echo I modified ~~BINGO~~"
+"""
+
+import optparse
+import os
+import subprocess
+import sys
+
+
+# List of C++-like source file extensions.
+_CPP_EXTENSIONS = ('h', 'hh', 'hpp', 'c', 'cc', 'cpp', 'cxx', 'mm',)
+
+
+def GitShell(args, ignore_return=False):
+  """A shell invocation suitable for communicating with git. Returns
+  output as list of lines, raises exception on error.
+  """
+  job = subprocess.Popen(args,
+                         shell=True,
+                         stdout=subprocess.PIPE,
+                         stderr=subprocess.STDOUT)
+  (out, err) = job.communicate()
+  if job.returncode != 0 and not ignore_return:
+    print out
+    raise Exception("Error %d running command %s" % (
+        job.returncode, args))
+  return out.split('\n')
+
+
+def FilenamesFromGit(branch_name, extensions):
+  """Provides a list of all new and modified files listed by [git diff
+  branch_name] where branch_name can be blank to get a diff of the
+  workspace.
+
+  Excludes deleted files.
+
+  If extensions is not an empty list, include only files with one of
+  the extensions on the list.
+  """
+  lines = GitShell('git diff --stat=600,500 %s' % branch_name)
+  filenames = []
+  for line in lines:
+    line = line.lstrip()
+    # Avoid summary line, and files that have been deleted (no plus).
+    if line.find('|') != -1 and line.find('+') != -1:
+      filename = line.split()[0]
+      if filename:
+        filename = filename.rstrip()
+        ext = filename.rsplit('.')[-1]
+        if not extensions or ext in extensions:
+          filenames.append(filename)
+  return filenames
+
+
+def ForAllTouchedFiles(branch_name, extensions, token, command):
+  """For each new or modified file output by [git diff branch_name],
+  run command with token replaced with the filename. If extensions is
+  not empty, do this only for files with one of the extensions in that
+  list.
+  """
+  filenames = FilenamesFromGit(branch_name, extensions)
+  for filename in filenames:
+    os.system(command.replace(token, filename))
+
+
+def main():
+  parser = optparse.OptionParser(usage=__doc__)
+  parser.add_option('-x', '--extensions', default='', dest='extensions',
+                    help='Limits to files with given extensions '
+                    '(comma-separated).')
+  parser.add_option('-c', '--cpp', default=False, action='store_true',
+                    dest='cpp_only',
+                    help='Runs your command only on C++-like source files.')
+  parser.add_option('-t', '--token', default='[[FILENAME]]', dest='token',
+                    help='Sets the token to be replaced for each file '
+                    'in your command (default [[FILENAME]]).')
+  parser.add_option('-b', '--branch', default='origin/master', dest='branch',
+                    help='Sets what to diff to (default origin/master). Set '
+                    'to empty to diff workspace against HEAD.')
+  opts, args = parser.parse_args()
+
+  if not args:
+    parser.print_help()
+    sys.exit(1)
+
+  extensions = opts.extensions
+  if opts.cpp_only:
+    extensions = _CPP_EXTENSIONS
+
+  ForAllTouchedFiles(opts.branch, extensions, opts.token, args[0])
+
+
+if __name__ == '__main__':
+  main()