title: Upper/Lower case discrepancy in Git and SourceTree
body: <p>I've been maintaining a repo via source tree and I've come across an issue where a single file seems to have two references to it – one in lowercase and one in uppercase.<br>
  This came about after I changed the case of the title a while back. If I try deleting one, both are removed, and if I try committing them both, one always remains in the working copy.</p>
  
  <p>I have tried <code>mv</code> on the file to see if I could force it to use just uppercase, but I still have the issue of the duplicate reference.</p>
  
  <p>If anyone has a solution (and an explanation of what is happening), I'd love to hear it.</p>