title: Retrieving versions of a file
body: <p>Say I have a path to a git repository in the local filesystem: <code>path_to_my_repository</code>, and a path to a file in the repository <code>path_to_file</code>.</p>
  
  <p>For a given list of dates, how can I get the corresponding version of the file on a particular branch <strong>from Python</strong> (i.e. loading the file in memory).</p>