revlog: reduce memory usage in addgroup
- use a buffer to extract the delta from a chunk
- avoid concatenating to a compressed delta
- use a buffer to directly extra full text from a trivial delta
- delete chunk and delta objects after use
<table class="logEntry parity#parity#">
<tr>
<th class="age">#date|age# ago:</th>
<th class="firstline">#desc|strip|firstline|escape#</th>
</tr>
<tr>
<th class="revision">changeset #rev#:</th>
<td class="node"><a href="#url#rev/#node|short#{sessionvars%urlparameter}">#node|short#</a></td>
</tr>
#parent%changelogparent#
#child%changelogchild#
#changelogtag#
<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>
<tr>
<th class="files"><a href="#url#file/#node|short#{sessionvars%urlparameter}">files</a>:</th>
<td class="files">#files#</td>
</tr>
</table>