title: Git Subtree only one file or directory
body: <p>I use Git Subtree like below:</p>
  
  <pre><code>git subtree add --prefix=directory_destination_path --squash git@bitbucket.org:kicaj/projectname.git master
  </code></pre>
  
  <p>But in path: <code>directory_destination_path</code> copy all repo from <code>projectname.git</code></p>
  
  <p>How to copy to <code>directory_destination_path</code> only subdirectory or only some file from <code>projectname.git</code> ?</p>
  
  <p><strong>EDIT:</strong><br>
  One more question:<br>
  How to update (automatic) files changes in both repositories were still the same? It is possible?</p>