I've had a problem running "fossil merge mainbranch", while in the upstream server (not in the local repository) there was a card that changed the "mainbranch" last checkin to a new branch, as you do with 'mistake'.

I use autosync on, and if "fossil merge mainbranch" had triggered a pull before merge, this problem would not have happened.

Do you find it reasonable to trigger a pull on merge?