Mode to automatically delete old messages

[geofft@mit.edu]

This is a ​suggestion from kchen on our UserVoice.

I think the intention here is so that you can get back to barnowl after a while and not have a huge backlog, and also not have consumed a large amount of memory in the process. "Old" can be defined by time, by number of messages, perhaps by amount of memory, etc.

ike comments that he wants to be able to do this on a per-filter basis, which I'd also find useful -- for instance, keep everything in my home filter indefinitely, but only the last few days of everything else I'm subscribed to.

[jgross@mit.edu]

I suspect that this can be done easily with the delete-and-expunge command, with a timer, in perl; for example, messages which are too old can be deleted every hour, or once a day, etc. There is still the question of what the interface should be; options I see include:

1. making a command which attaches or detaches such a timer to a filter (or for all messages), with all of the state living in perl
2. making two variables, one which specifies a filter, and the other of which specifies a number of hours (or days) messages matching that filter should stick around before being automatically deleted.