split automagically an ancient group into archives

[Sébastien Kirche]

Hi,

I use to archive my sent messages into an nnml archive group.
It is set with the following :
(setq gnus-message-archive-group
          '((if (message-news-p)
                        (concat "nnml+archives:News-sent." (format-time-string 
"%Y-%m"))
                  (concat "nnml+archives:Mail-sent." (format-time-string 
"%Y-%m"))
                )))

Now I am accessing an old sent  group of my former MUA via nnmh backend;
it contains several  years that I need to keep. How  could I merge these
messages in my current nnml+archives ?

I would prefer a bit a of  code to evaluate into the scratch buffer than
manually  limiting the  display  of the  nnmh  group then  moving, in  a
repetitive way.

Could someone help me ? Thanks.
-- 
Sébastien Kirche