title: How to force reformat file with black code formatter
body: <p>I have a file in a git repo that is not reformatted for reason <code>wasn't modified on disk since last run.</code>
  But eventually, a change is made in the file e.g new line. And a whole lot of major reformatting is done by black.
  The file seems to have pending reformatting work which is not detected because it hasn't been modified.</p>
  <p>How do I force black to reformat/check a file regardless of whether it has been modified since last run?</p>