title: Single file as Git submodule
body: <p>I'm trying to ascertain best-practices for shared code amongst Git repositories.</p>
  
  <p>So far, I've obviously come across submodules which seem like they - almost - fit the bill. My project is a PHP MVC framework with a simple structure:</p>
  
  <ul>
  <li>/app</li>
  <li>core.php</li>
  <li>/core</li>
  </ul>
  
  <p>Where <code>app</code> is a folder containing application-specific controllers, models, views etc. while <code>core</code> contains those of general use, e.g. a login controller. The <code>core.php</code> file itself is the global handler for all requests.</p>
  
  <p>As such, the shared code amongst all of my deployments of this MVC framework is <code>core.php</code> and <code>core</code>.</p>
  
  <p>I can see how it is possible to turn <code>core</code> into a Git submodule, but not <code>core.php</code>.</p>
  
  <p>Is this even possible? Do I need to re-architecture my framework so that <code>core.php</code> resides inside the <code>core</code> folder so I can make the whole folder a submodule, or is there a better way?</p>