title: Git: how to add a file but not track it
body: <p>In our .gitignore file we have <code>database.php</code> because it's a db config file which needs to be specific to each developer's local installation. However, every time I checkout the branch I have to recreate that file. It sucks.</p>
  
  <p>How do I add the file so that it doesn't disappear every time, but also isn't tracked?</p>