Gnus doesn't update nntp marks files when unplugged

[Katsumi Yamaoka <yamaoka@jpl.org>]

Hi,

Sin'ya Kanematsu reported that .marks files for nntp groups
aren't updated when Gnus is unplugged.  He usually do the
following:

1. Make sure Gnus is plugged (type `J j' if needed).
2. Type `g'.
3. Type `J s'.
4. Type `J j' to make Gnus be unplugged; type `s' to save.
5. Select a group of which the level is 1 using the `=' key. [*]
6. Read articles that have been downloaded; type `@' to instruct
   Gnus to download new articles. [**]
7. Exit the group.
8. Do 5,6,7 repeatedly.

[*] He has set `gnus-agent-handle-level' to 2, though he doesn't
 have group of which the level is 2.
[**] He has set it up not to download articles by default
 because of a lot of spam.

Although I'm not familiar with unplugged operations, I also
confirmed .marks files for nntp groups aren't updated when
Gnus is unplugged.  I did:

1. Make sure Gnus is plugged.
2. Type `J u' on a group in which there're unread articles.
3. Type `J j' to make Gnus be unplugged and read articles in the
 group in question.
4. Check whether the .marks file is updated.

Is there a thing that we need to do further?  Or is it simply a
bug?

Thanks in advance.