Set<String> oldLnks;
if (oldRevId != -1 && oldPage != null && oldPage.getCurRev() != null) {
// get a list of previous categories and templates:
wikiModel.setUp();
final long timeAtRenderStart = System.currentTimeMillis();
wikiModel.render(null, oldPage.getCurRev().unpackedText());
timeAtStart -= (System.currentTimeMillis() - timeAtRenderStart);
// note: no need to normalise the pages, we will do so during the write/read key generation
oldCats = wikiModel.getCategories().keySet();
oldTpls = wikiModel.getTemplates();
if (Options.WIKI_USE_BACKLINKS) {