nnshimbun-request-scan fetches unsubscribed server groups

[Matt Lundin <mdl@xxxxxxxxxxxx>]

With the most recent nognus (44e4398abd1f2d11b3f32d64c54a6366104cf485),
all nnshimbun groups in a server are fetched at startup, regardless of
whether one has subscribed to them or not. For instance, I subscribe to
a single group in sb-nytimes, but, at startup, the nognus fetches and
generates nov databases for all the rss feeds for all groups defined in
the module (quite a few).

I asked about this on the gnus development list and I have been advised
that the "new" gnus calls nnshimbun-request-scan without a group
parameter:

http://permalink.gmane.org/gmane.emacs.gnus.general/72202

Note: a previous fix for this problem in gnus-start.el was reverted
because it seems to have caused problems for other backends:

http://permalink.gmane.org/gmane.emacs.gnus.general/72195

Looking at nnshimbun-request-scan, I see that if the group parameter is
nil, nnshimbun calls shimbun-groups to find *all* groups defined in the
server rather than only subscribed groups. Would it be possible for
nnshimbun-request-scan to generate nov databases only for the server's
subscribed groups?

I.e., instead of using...

(shimbun-groups nnshimbun-shimbun)

...to generate the list of groups (line 529 in nnshimbun.el), is there a
function that might return only the subscribed groups on the server?

Thank you,
Matt