Add revlog.parentrevs function.
This allows one to walk the revision graph using only revision numbers,
which can be faster than using revision hashes, especially for
RevlogNG, where the parents of a revision are stored as revision
numbers.
<table class="logEntry parity#parity#">
<tr>
<th class="age">#date|age# ago:</th>
<th class="firstline"><a href="?cs=#node|short#">#desc|strip|firstline|escape#</a></th>
</tr>
<tr>
<th class="revision">revision #filerev#:</td>
<td class="node">
<a href="?f=#filenode|short#;file=#file|urlescape#">#filenode|short#</a>
<a href="?fd=#node|short#;file=#file|urlescape#">(diff)</a>
<a href="?fa=#filenode|short#;file=#file|urlescape#">(annotate)</a>
</td>
</tr>
#rename%filelogrename#
<tr>
<th class="author">author:</th>
<td class="author">#author|obfuscate#</td>
</tr>
<tr>
<th class="date">date:</th>
<td class="date">#date|date#</td>
</tr>
</table>