Calls clang-apply-fixes on a given directory.

def apply_fixes(args, tmpdir):
  """Calls clang-apply-fixes on a given directory."""
  invocation = [args.clang_apply_replacements_binary]
  if args.format:
    invocation.append('-format')
  if args.style:
    invocation.append('-style=' + args.style)
  invocation.append(tmpdir)
  subprocess.call(invocation)