title: How to extract one file with commit history from a Git repo with index-filter & co?
body: <p>I have a Git repo converted from SVN to Mercurial to Git, and I wanted to extract just one source file. I also had weird characters like <code>aÌ</code> (an encoding mismatch corrupted Unicode <code>ä</code>) and spaces in the filenames.</p>
  <p>How can I extract one file from a repository and place it at the root of the new repo?</p>