folder_format: reporting new/unread/read totals?

[amacleod@xxxxxxxx (Allister MacLeod)]

Greetings, 
    
    I'd like mutt to start up showing me a screen listing all my
defined mailboxes, along with an indicator showing how many new
messages are in each box, along with the total number of messages in
the box.  It looks like IMAP folders supply the "new" amount in place
of the %N field, but I could not find anything documented about old
messages or read messages.

Ideally, I would want to see:
  %m - total messages in the folder
  %N - number of new messages (that are flagged with N in the index)
  %O - number of old unread messages (flagged with O in index)
  %R - number of read messages (flagged with a space)

Then I'd set folder_format="[%3N/%3O/%4m] %f"
to get something like
   [  1/  0/   1] INBOX
   [  0/ 12/ 107] INBOX.LISTS.mutt

    So, I'd gladly welcome advice/patches from anyone who has more
experience delving the mutt source than me.  I'm willing to get my
hands dirty.. I just don't know how deep I might have to go to get
this sort of thing to work.  And, if somebody knows that it's
implemented or easy to implement, but not yet documented in the
manual, please let me know.

Thanks,
 Allister