Please release an 6.4.x update due to upstream Mercurial bug
There is a serious issue in Mercurial 6.4.2 (see http://markmail.org/message/ecgbcqjt3pn6dww4 or https://repo.mercurial-scm.org/hg/rev/a445194f0a4d) breaking some repositories.
Could you please release a new version containing that bugfix?