R1:14c516b7a109

Updating the filtering of Mercurial debug output

Summary:
With newer versions of Mercurial come newer debug messages which need filtered out.

1. In the scenario of Phabricator observing a hosted Mercurial repository which exists on a server in a multi-user environment it's possible that a repository computes branch cache at a tip revision which is not present. When this happens Mercurial will include in the debug output this information. This message indicates that the cache is going to be re-computed.