IMAP and nnmail splitting

[Julien Cubizolles]

I'm trying to split the mail I get on an IMAP server but the behaviour
is not what I would expect. I'm using nnmail-split-fancy. 

* The nnimap backend is not automatically splitted, I have to use B r in
  the summary buffer. From the doc  :
,----
| By default, splitting is performed on all incoming messages. If you
| specify a directory entry for the variable mail-sources (see Mail
| Source Specifiers), however, then splitting does not happen by
| default.
`----
 I didn't specify any mail source (maybe I should have but I didn't
  really understand the difference between choosing a select method and
  a mail source) so I gather the splitting should take place.


* I'm using nnmail splitting instead of nnimap splitting because I want
  the splitted mail to be saved on my computer. That's what happens but
  a copy stays on the IMAP server so I end up with two unread mails. Is
  that intended ? How could I mark the mail left on the IMAP server read
  so it's skipped when reading mail ?

  Here is the relevant part of my .gnus.el
  ,----
  | (setq nnmail-split-fancy
  |    `(|
  |         (: gnus-registry-split-fancy-with-parent)
  |         (: spam-split 'spam-use-bogofilter)
  | 
  |         (any "some regexp" "some group")
  |         
  |         ("gnus-warning" "duplicat\\(e\\|ion\\) of message" "duplicate")
  |          "mail.misc"
  |              )
  | )
  `----

* I'd like to be able to have splitting something between nnmail-split
  and nnimap-split : mail matching some condition would be split