Make compare links use oldids.

templates/index.mako

@@ -219,7 +219,7 @@
                                 % if i == 0:
                                     <a href="#cv-chain-table">Compare</a>
                                 % else:
-                                    <a href="${request.url | httpsfix, h}&amp;action=compare&amp;url=${source.url | u}">Compare</a>
+                                    <a href="${request.script_root | h}?lang=${query.lang | h}&amp;project=${query.project | h}&amp;oldid=${query.oldid or query.page.lastrevid | h}&amp;action=compare&amp;url=${source.url | u}">Compare</a>
                                 % endif
                             </td>
                         </tr>