I installed the jobconfighistory-plugin (nice), then I deleted some jobs.
I had assumed that I would end up with a deleted-job entry that contained a copy of the job just prior to deletion. What I actually ended up with was just a deleted-job entry.
[Fortunately, for these jobs, that's fine].
It looks to me (from an admittedly cursory look at the code) as though FileHistoryDao.deleteItem(Item) saves the history of the job. So I think that if, between installing the plugin and deleting the job, I had made any changes to the job, those would have created history entries that included a copy of the job, and then when I deleted the job all of that would have been saved. (Right?)
Quite likely that's good enough and it doesn't really make sense to do anything about the corner case that I found, or perhaps it's even the intended behaviour, but I'm logging it just in case.