Add clang-format-diff.py

Turns out this script was never checked in, causing the check_code_format.sh script to
never run. This is due to python *not* returning an error when it fails to find the
python script, which results in the shell script passing while never actually checking
the formatting.

scripts/clang-format-diff.py

@@ -0,0 +1,123 @@
+#!/usr/bin/env python
+#
+#===- clang-format-diff.py - ClangFormat Diff Reformatter ----*- python -*--===#
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===------------------------------------------------------------------------===#
+
+"""
+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 --no-color HEAD^ | clang-format-diff.py -p1 -i
+  svn diff --diff-cmd=diff -x-U0 | clang-format-diff.py -i
+
+"""
+from __future__ import absolute_import, division, print_function
+
+import argparse
+import difflib
+import re
+import subprocess
+import sys
+
+if sys.version_info.major >= 3:
+    from io import StringIO
+else:
+    from io import BytesIO as StringIO
+
+
+def main():
+  parser = argparse.ArgumentParser(description=__doc__,
+                                   formatter_class=
+                                           argparse.RawDescriptionHelpFormatter)
+  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|hh|hpp|m|mm|inc|js|ts|proto'
+                      r'|protodevel|java|cs)',
+                      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)')
+  parser.add_argument('-binary', default='clang-format',
+                      help='location of binary to use for clang-format')
+  args = parser.parse_args()
+
+  # Extract changed lines for each file.
+  filename = None
+  lines_by_file = {}
+  for line in sys.stdin:
+    match = re.search(r'^\+\+\+\ (.*?/){%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(r'^@@.*\+(\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.items():
+    if args.i and args.verbose:
+      print('Formatting {}'.format(filename))
+    command = [args.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,
+                         universal_newlines=True)
+    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(stdout).readlines()
+      diff = difflib.unified_diff(code, formatted_code,
+                                  filename, filename,
+                                  '(before formatting)', '(after formatting)')
+      diff_string = ''.join(diff)
+      if len(diff_string) > 0:
+        sys.stdout.write(diff_string)
+
+if __name__ == '__main__':
+  main()