How to tell Rubocop to ignore a specific directory or file
<p>My project is extending open-source classes from a third-party gem that we don't want to hold to the same coding standards as our own code.  Refactoring the gem code isn't a viable option.  We just want Rubocop to ignore the copied code.</p>

<p>How can I instruct Rubocop to completely ignore a file or directory?</p>