As of a few minutes ago we have broken the long retained backwards compatibility on our databases.
Anyone using SVN revision 1462 or later (so also upcoming 1.7.23) will be unable to roll back to a previous version because the nick.db written by our latest builds will be incompatible. So when trying out SVN, be sure to make backups of nick.db before starting anope.
Anope-1.7.23 (or currently last SVN) should read all older databases, but right after loading will overwrite the nick.db with a newer version of the database which, once written will be unable to load in 1.7.22 (or SVN 1461) or earlier.
The above is also valid for the pre nickserv database (pre-nick.db) which stores not yet verified accounts when email activation is enabled.
The decision to drop backwards compatibility wasn't taken lightly, yet it was the only way to fix a bug in the database system causing sha1 hashes of nickserv passes to be stored incorrectly.
Also note that this fix doesn't work backwards.. already broken password hashes will not magically be fixed, they will need to be reset, once that is done the DB should contain the correct hash.
Feedback on Anope-SVN is currently very welcome as this is a rather big change. Especially feedback about the effects on MySQL (both dump only and RDB) is welcome.