Fix for ietf-tools#467.

 - Legacy-Id: 2628

Author: larseggert

lars/ietf/templates/idrfc/doc_diffs.html

@@ -34,7 +34,7 @@
 
 <div class="ietf-box diffTool">
 <h2 style="margin-top:0;margin-bottom:4px;">Diffs</h2>
-<form action="http://tools.ietf.org/rfcdiff" method="get" target="_blank" style="margin:0;">
+<form action="http{% if request.is_secure %}s{% endif %}://tools.ietf.org/rfcdiff" method="get" target="_blank" style="margin:0;">
 <table>
 <tr><td>
 <label>From:</label> <select name="url1">