title: Pytest won't accept argument starting with ../../
body: <p>I have added a custom command line argument --dll but when I supply a path starting with ../../ it doesn't recognize the argument:</p>
  <pre><code># pytest --dll ../../lib.dll
  ERROR: usage: pytest [options] [file_or_dir] [file_or_dir] [...]
  pytest: error: unrecognized arguments: --dll
  </code></pre>
  <p>However it works if I type &quot;--dll=../../lib.dll&quot;, &quot;--dll ../lib.dll&quot; or put another argument before.</p>
  <p>Why is this and is it pytest specific?</p>
  <p>I'm running this from Cygwin with Cygwin's python.</p>