revlog: use the `entry` function in bundlerepo
We can use some of the default value again!
Differential Revision: https://phab.mercurial-scm.org/D10796
{header}
<id>{urlbase}{url|urlescape}</id>
<link rel="self" href="{urlbase}{url|urlescape}atom-branches"/>
<link rel="alternate" href="{urlbase}{url|urlescape}branches"/>
<title>{repo|escape}: branches</title>
<summary>{repo|escape} branch history</summary>
<author><name>Mercurial SCM</name></author>
{latestentry%feedupdated}
{entries%branchentry}
</feed>