new_contents: # This file is a minimal clang-format vim-integration. To install:
  # - Change 'binary' if clang-format is not on the path (see below).
  # - Add to your .vimrc:
  #
  #   map <C-I> :pyf <path-to-this-file>/clang-format.py<cr>
  #   imap <C-I> <c-o>:pyf <path-to-this-file>/clang-format.py<cr>
  #
  # The first line enables clang-format for NORMAL and VISUAL mode, the second
  # line adds support for INSERT mode. Change "C-I" to another binding if you
  # need clang-format on a different key (C-I stands for Ctrl+i).
  #
  # With this integration you can press the bound key and clang-format will
  # format the current line in NORMAL and INSERT mode or the selected region in
  # VISUAL mode. The line or region is extended to the next bigger syntactic
  # entity.
  #
  # It operates on the current, potentially unsaved buffer and does not create
  # or save any files. To revert a formatting, just undo.
  
  import difflib
  import json
  import subprocess
  import sys
  import vim
  
  # set g:clang_format_path to the path to clang-format if it is not on the path
  # Change this to the full path if clang-format is not on the path.
  binary = 'clang-format'
  if vim.eval('exists("g:clang_format_path")') == "1":
    binary = vim.eval('g:clang_format_path')
  
  # Change this to format according to other formatting styles. See the output of
  # 'clang-format --help' for a list of supported styles. The default looks for
  # a '.clang-format' or '_clang-format' file to indicate the style that should be
  # used.
  style = 'file'
  fallback_style = None
  if vim.eval('exists("g:clang_format_fallback_style")') == "1":
    fallback_style = vim.eval('g:clang_format_fallback_style')
  
  def main():
    # Get the current text.
    buf = vim.current.buffer
    text = '\n'.join(buf)
  
    # Determine range to format.
    lines = '%s:%s' % (vim.current.range.start + 1, vim.current.range.end + 1)
  
    # Determine the cursor position.
    cursor = int(vim.eval('line2byte(line("."))+col(".")')) - 2
    if cursor < 0:
      print 'Couldn\'t determine cursor position. Is your file empty?'
      return
  
    # Avoid flashing an ugly, ugly cmd prompt on Windows when invoking clang-format.
    startupinfo = None
    if sys.platform.startswith('win32'):
      startupinfo = subprocess.STARTUPINFO()
      startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
      startupinfo.wShowWindow = subprocess.SW_HIDE
  
    # Call formatter.
    command = [binary, '-lines', lines, '-style', style, '-cursor', str(cursor)]
    if fallback_style:
      command.extend(['-fallback-style', fallback_style])
    if vim.current.buffer.name:
      command.extend(['-assume-filename', vim.current.buffer.name])
    p = subprocess.Popen(command,
                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                         stdin=subprocess.PIPE, startupinfo=startupinfo)
    stdout, stderr = p.communicate(input=text)
  
    # If successful, replace buffer contents.
    if stderr:
      print stderr
  
    if not stdout:
      print ('No output from clang-format (crashed?).\n' +
          'Please report to bugs.llvm.org.')
    else:
      lines = stdout.split('\n')
      output = json.loads(lines[0])
      lines = lines[1:]
      sequence = difflib.SequenceMatcher(None, vim.current.buffer, lines)
      for op in reversed(sequence.get_opcodes()):
        if op[0] is not 'equal':
          vim.current.buffer[op[1]:op[2]] = lines[op[3]:op[4]]
      vim.command('goto %d' % (output['Cursor'] + 1))
  
  main()
  
subject: Add clang-format.py.