hgweb: partially revert 4ec58b157265 The change from self.repo.ui.diffopts() to ui.diffopts() causes a traceback when the diff of a changeset should be displayed in the web interface. Revert to self.repo.ui.diffopts() for now.

Content-type: text/xml

<rss version="2.0">
  <channel>
    <link>#url#</link>
    <language>en-us</language>