Provide the exact count of article numbers in GROUP-like commands

[Julien-Elie]

To provide a solution to the recurring question about the estimated vs real count of articles (especially in empty newsgroups).

I suggest the following things:

• add an inn.conf parameter like groupexactcount (defaulting to 5)
• if the estimated count known by nnrpd when responding to GROUP, LISTGROUP and LIST COUNTS commands is inferior to groupexactcount, then nnrpd really counts the exact number of articles still present in the newsgroup, and gives that number
• if groupexactcount is set to 1, then nnrpd will always give the estimated number, and never count the real number (current behaviour)
• if groupexactcount is set to 0, then nnrpd will always give the exact count

This way, without a real penalty in performance, we handle the case of empty newsgroups better.

Low watermarks and high watermarks are kept untouched (and may not correspond to existing articles), so that to allow possible reinstatements of articles.

[Julien-Elie]

Paolo suggested when discussing it in April 2020 on news.software.nntp (\news:r64ihl$1ns$1@gioia.aioe.org\) that the parameter be in readers.conf access groups instead. It would permit having a finer control on the connections to which groupexactcount applies (only to localhost connections for instance, for the sake of scripts, and not everyone). Maybe we could have both (inn.conf to set a default, and a possibility to override it in readers.conf).

[Julien-Elie]

@Aioe, @yamo-nntp, this feature is now available. At last! 😄 You're the two ones who have recently spoken about it. Local scripts and Newsportal will now have access to the right count of articles, which notably permits not advertising available articles in the estimate count of empty newsgroups.

Previously:

GROUP trigofacile.test
211 1 5 5 trigofacile.test

Now:

GROUP trigofacile.test
211 0 6 5 trigofacile.test

LIST COUNTS trigofacile.test
215 Newsgroups in form "group high low count status"
trigofacile.test 5 6 0 y
.

LISTGROUP trigofacile.test
211 0 6 5 trigofacile.test
.