Bitbucket will kill all its Mercurial repositories on 01-Jul-2020, see also:

• Official announcement: https://bitbucket.org/blog/sunsetting-mercurial-support-in-bitbucket
• Summary of the affair and offer by a different provider: https://www.perforce.com/blog/vcs/bitbucket-mercurial-support-ending

It is the responsibility of the AFP editors to come up with a plan that fits to the underlying technology: Isabelle with its existing tooling for Mercurial (e.g. for long-term test data, paring of Isabelle vs. AFP changeset ids).