hgweb: add guid to rss items

templates/rss/changelogentry.tmpl

@@ -1,6 +1,6 b''
 <item>
     <title>#desc|strip|firstline|strip|escape#</title>
-    <link>{urlbase}{url}rev/{node|short}</link>
+    <guid isPermaLink="true">{urlbase}{url}rev/{node|short}</guid>
     <description><![CDATA[#desc|strip|escape|addbreaks#]]></description>
     <author>#author|obfuscate#</author>
     <pubDate>#date|rfc822date#</pubDate>

templates/rss/error.tmpl

@@ -4,6 +4,7 b''
     <item>
       <title>Error</title>
       <description>{error|escape}</description>
+      <guid>http://www.selenic.com/mercurial/#error</guid>
     </item>
   </channel>
 </rss>