support nested repositories.
mercurial will not recurse into a subdirectory that contains a .hg
directory. it is treated as a separate repository.
<item>
<title>#desc|strip|firstline|strip|escape#</title>
<link>#url#?f=#filenode|short#;file=#file|urlescape#</link>
<description><![CDATA[#desc|strip|escape|addbreaks#]]></description>
<author>#author|obfuscate#</author>
<pubDate>#date|rfc822date#</pubDate>>
</item>