Block Googlebot from crawling certain slow useless URLs. Sometimes
Googlebot tries to crawl old source:<url>, approver:<name>, and
ordfav:<name> searches in bulk, which tends to slow down the site because
things like source:<url> are inherently slow, and because Google spends
hours at a time crawling them in parallel. This is despite the fact that
these links are already marked as nofollow and noindex, and source:<url>
links were removed from posts a long time ago to try to stop Google from
crawling them.
91587aeb6b