exchange: abort on pushing bookmarks pointing to secret changesets (issue6159) Until now, if there is a bookmark points to a changeset which is in secret phase, hg will push the bookmark, but not the changeset referenced by that bookmark. This leaves the server bookmarks in a bad state, because that bookmark now points to a revision that does not exist on the server. This patch makes hg to abort on such cases. Differential Revision: https://phab.mercurial-scm.org/D6731

tests: add test to demonstrate issue6159 Differential Revision: https://phab.mercurial-scm.org/D6740

packaging: add Bullseye, remove Jessie Jessie is oldoldstable now, and Bullseye is going to be the next stable (now testing). We're continuing to support the current oldstable, stable and testing releases. Differential Revision: https://phab.mercurial-scm.org/D6762