If you’d like to read the parent of the current article, and it is not
displayed in the summary buffer, you might still be able to. That is,
if the current group is fetched by NNTP, the parent hasn’t expired
and the References in the current article are not mangled, you
can just press ^ or A r
(gnus-summary-refer-parent-article). If everything goes well,
you’ll get the parent. If the parent is already displayed in the
summary buffer, point will just move to this article.
If given a positive numerical prefix, fetch that many articles back into the ancestry. If given a negative numerical prefix, fetch just that ancestor. So if you say 3 ^, Gnus will fetch the parent, the grandparent and the great-grandparent of the current article. If you say -3 ^, Gnus will only fetch the great-grandparent of the current article.
Fetch all articles mentioned in the References header of the
article (gnus-summary-refer-references).
Display the full thread where the current article appears
(gnus-summary-refer-thread). By default this command looks for
articles only in the current group. Some backends (currently only
nnimap) know how to find articles in the thread directly. In
other cases each header in the current group must be fetched and
examined, so it usually takes a while. If you do it often, you may
consider setting gnus-fetch-old-headers to invisible
(see Filling In Threads). This won’t have any visible effects
normally, but it’ll make this command work a whole lot faster. Of
course, it’ll make group entry somewhat slow.
If gnus-refer-thread-use-search is non-nil then those backends
that know how to find threads directly will search not just in the
current group but all groups on the same server.
The gnus-refer-thread-limit variable says how many old (i.e.,
articles before the first displayed in the current group) headers to
fetch when doing this command. The default is 200. If t, all
the available headers will be fetched. This variable can be overridden
by giving the A T command a numerical prefix.
In most cases gnus-refer-thread adds any articles it finds to
the current summary buffer. (When gnus-refer-thread-use-search
is true and the initial referral starts from a summary buffer for a
non-virtual group this may not be possible. In this case a new
summary buffer is created holding a virtual group with the result of
the thread search.) If gnus-refer-thread-limit-to-thread is
non-nil then the summary buffer will be limited to articles in the
thread.
You can also ask Gnus for an arbitrary article, no matter what group it
belongs to. M-^ (gnus-summary-refer-article) will ask you
for a Message-ID, which is one of those long, hard-to-read
thingies that look something like ‘<38o6up$6f2@hymir.ifi.uio.no>’.
You have to get it all exactly right. No fuzzy searches, I’m afraid.
Gnus looks for the Message-ID in the headers that have already
been fetched, but also tries all the select methods specified by
gnus-refer-article-method if it is not found.
If the group you are reading is located on a back end that does not
support fetching by Message-ID very well (like nnspool),
you can set gnus-refer-article-method to an NNTP method. It
would, perhaps, be best if the NNTP server you consult is the one
updating the spool you are reading from, but that’s not really
necessary.
It can also be a list of select methods, as well as the special symbol
current, which means to use the current select method. If it
is a list, Gnus will try all the methods in the list until it finds a
match.
Here’s an example setting that will first try the current method, and then ask Google if that fails:
(setq gnus-refer-article-method
'(current
(nnweb "google" (nnweb-type google))))
Most of the mail back ends support fetching by Message-ID, but
do not do a particularly excellent job at it. That is, nnmbox,
nnbabyl, nnmaildir, nnml, are able to locate
articles from any groups, while nnfolder, and nnimap are
only able to locate articles that have been posted to the current
group. nnmh does not support this at all.
Fortunately, the special nnregistry back end is able to locate
articles in any groups, regardless of their back end (see fetching by Message-ID using the
registry).