changeset_printer: use node.wdirrev to calculate meaningful parentrevs
Because we defined the working-directory revision is INT_MAX, it makes sense
that "hg log -r 'wdir()'" displays the "parent:" field. This is the same for
two revisions that are semantically contiguous but the intermediate revisions
are hidden.
<entry>
<title>{branch|escape}</title>
<link rel="alternate" href="{urlbase}{url|urlescape}rev/{node|short}"/>
<id>{urlbase}{url|urlescape}#branch-{node}</id>
<updated>{date|rfc3339date}</updated>
<published>{date|rfc3339date}</published>
<content type="text"><![CDATA[{branch|strip|escape|addbreaks}]]></content>
</entry>