localrepo: improve readability of _findtags(), readtags() (issue548).
- rename many local variables
- add some comments
- refactor call to line.split() (catch ValueError rather
than checking length of return value: one less local variable)
<entry>
<title>{desc|strip|firstline|strip|escape|nonempty}</title>
<id>{urlbase}{url}#changeset-{node}</id>
<link href="{urlbase}{url}rev/{node}"/>
<author>
<name>{author|person|escape}</name>
<email>{author|email|obfuscate}</email>
</author>
<updated>{date|rfc3339date}</updated>
<published>{date|rfc3339date}</published>
<content type="xhtml">
<div xmlns="http://www.w3.org/1999/xhtml">
<pre xml:space="preserve">{desc|escape|nonempty}</pre>
</div>
</content>
</entry>