bug#61325: 30.0.50; Jokes in GNUS manual

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Richard Stallman <rms@gnu.org> writes:

> [[[ To any NSA and FBI agents reading my email: please consider    ]]]
> [[[ whether defending the US Constitution against all enemies,     ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
>
>   > A kill file (also killfile, bozo bin or twit list) is a file used
>   > by some Usenet reading programs to discard articles matching some
>   > unwanted patterns of subject, author, or other header
>   > lines. Adding a person or subject to one's kill file means that
>   > person or topic will be ignored by one's newsreader in the
>   > future. By extension, the term may be used for a decision to
>   > ignore the person or subject in other media.
>
> I see.  But the manual has to tell the reader this, if it mentions
> kill files at all.
>
>   > More advanced newsreader software like Gnus sometimes provides a
>   > more sophisticated form of filter known as scoring, where score
>   > files are maintained which use fuzzy logic to apply arbitrarily
>   > complex overlapping sets of rules to score articles up or down,
>   > with articles being properly killed (ignored by the newsreader)
>   > only when their weighted score drops below a user-defined
>   > threshold.
>
> That seems like a useful feature.  But the GNUS manual has to explain it.

And, it does...

8.13 Kill Files
===============

Gnus still supports those pesky old kill files.  In fact, the kill file
entries can now be expiring, which is something I wrote before Daniel
Quinlan thought of doing score files, so I’ve left the code in there.

   In short, kill processing is a lot slower (and I do mean _a lot_)
than score processing, so it might be a good idea to rewrite your kill
files into score files.

   Anyway, a kill file is a normal ‘emacs-lisp’ file.  You can put any
forms into this file, which means that you can use kill files as some
sort of primitive hook function to be run on group entry, even though
that isn’t a very good idea.

   Normal kill files look like this:

     (gnus-kill "From" "Lars Ingebrigtsen")
     (gnus-kill "Subject" "ding")
     (gnus-expunge "X")

   This will mark every article written by me as read, and remove the
marked articles from the summary buffer.  Very useful, you’ll agree.

   Other programs use a totally different kill file syntax.  If Gnus
encounters what looks like a ‘rn’ kill file, it will take a stab at
interpreting it.

   Two summary functions for editing a GNUS kill file:

‘M-k’
     Edit this group’s kill file (‘gnus-summary-edit-local-kill’).

‘M-K’
     Edit the general kill file (‘gnus-summary-edit-global-kill’).

   Two group mode functions for editing the kill files:

‘M-k’
     Edit this group’s kill file (‘gnus-group-edit-local-kill’).

‘M-K’
     Edit the general kill file (‘gnus-group-edit-global-kill’).

   Kill file variables:

‘gnus-kill-file-name’
     A kill file for the group ‘soc.motss’ is normally called
     ‘soc.motss.KILL’.  The suffix appended to the group name to get
     this file name is detailed by the ‘gnus-kill-file-name’ variable.
     The “global” kill file (not in the score file sense of “global”, of
     course) is just called ‘KILL’.

‘gnus-kill-save-kill-file’
     If this variable is non-‘nil’, Gnus will save the kill file after
     processing, which is necessary if you use expiring kills.

‘gnus-apply-kill-hook’
     A hook called to apply kill files to a group.  It is
     ‘(gnus-apply-kill-file)’ by default.  If you want to ignore the
     kill file if you have a score file for the same group, you can set
     this hook to ‘(gnus-apply-kill-file-unless-scored)’.  If you don’t
     want kill files to be processed, you should set this variable to
     ‘nil’.

‘gnus-kill-file-mode-hook’
     A hook called in kill-file mode buffers.


8.4 Score File Format
=====================

A score file is an ‘emacs-lisp’ file that normally contains just a
single form.  Casual users are not expected to edit these files;
everything can be changed from the summary buffer.

   Anyway, if you’d like to dig into it yourself, here’s an example:

     (("from"
       ("Lars Ingebrigtsen" -10000)
       ("Per Abrahamsen")
       ("larsi\\|lmi" -50000 nil R))
      ("subject"
       ("Ding is Badd" nil 728373))
      ("xref"
       ("alt.politics" -1000 728372 s))
      ("lines"
       (2 -100 nil <))
      (mark 0)
      (expunge -1000)
      (mark-and-expunge -10)
      (read-only nil)
      (orphan -10)
      (adapt t)
      (files "/hom/larsi/News/gnu.SCORE")
      (exclude-files "all.SCORE")
      (local (gnus-newsgroup-auto-expire t)
             (gnus-summary-make-false-root empty))
      (eval (ding)))

   This example demonstrates most score file elements.  *Note Advanced
Scoring::, for a different approach.

   Even though this looks much like Lisp code, nothing here is actually
‘eval’ed.  The Lisp reader is used to read this form, though, so it has
to be valid syntactically, if not semantically.

   Six keys are supported by this alist:

‘STRING’
     If the key is a string, it is the name of the header to perform the
     match on.  Scoring can only be performed on these eight headers:
     ‘From’, ‘Subject’, ‘References’, ‘Message-ID’, ‘Xref’, ‘Lines’,
     ‘Chars’ and ‘Date’.  In addition to these headers, there are three
     strings to tell Gnus to fetch the entire article and do the match
     on larger parts of the article: ‘Body’ will perform the match on
     the body of the article, ‘Head’ will perform the match on the head
     of the article, and ‘All’ will perform the match on the entire
     article.  Note that using any of these last three keys will slow
     down group entry _considerably_.  The final “header” you can score
     on is ‘Followup’.  These score entries will result in new score
     entries being added for all follow-ups to articles that matches
     these score entries.

     Following this key is an arbitrary number of score entries, where
     each score entry has one to four elements.

       1. The first element is the “match element”.  On most headers
          this will be a string, but on the Lines and Chars headers,
          this must be an integer.

       2. If the second element is present, it should be a number—the
          “score element”.  This number should be an integer in the
          neginf to posinf interval.  This number is added to the score
          of the article if the match is successful.  If this element is
          not present, the ‘gnus-score-interactive-default-score’ number
          will be used instead.  This is 1000 by default.

       3. If the third element is present, it should be a number—the
          “date element”.  This date says when the last time this score
          entry matched, which provides a mechanism for expiring the
          score entries.  It this element is not present, the score
          entry is permanent.  The date is represented by the number of
          days since December 31, 1 BCE.

       4. If the fourth element is present, it should be a symbol—the
          “type element”.  This element specifies what function should
          be used to see whether this score entry matches the article.
          What match types that can be used depends on what header you
          wish to perform the match on.

          “From, Subject, References, Xref, Message-ID”
               For most header types, there are the ‘r’ and ‘R’
               (regexp), as well as ‘s’ and ‘S’ (substring) types, and
               ‘e’ and ‘E’ (exact match), and ‘w’ (word match) types.
               If this element is not present, Gnus will assume that
               substring matching should be used.  ‘R’, ‘S’, and ‘E’
               differ from the others in that the matches will be done
               in a case-sensitive manner.  All these one-letter types
               are really just abbreviations for the ‘regexp’, ‘string’,
               ‘exact’, and ‘word’ types, which you can use instead, if
               you feel like.

          “Extra”
               Just as for the standard string overview headers, if you
               are using gnus-extra-headers, you can score on these
               headers’ values.  In this case, there is a 5th element in
               the score entry, being the name of the header to be
               scored.  The following entry is useful in your
               ‘all.SCORE’ file in case of spam attacks from a single
               origin host, if your NNTP server tracks
               ‘NNTP-Posting-Host’ in overviews:

                    ("111.222.333.444" -1000 nil s
                     "NNTP-Posting-Host")

          “Lines, Chars”
               These two headers use different match types: ‘<’, ‘>’,
               ‘=’, ‘>=’ and ‘<=’.

               These predicates are true if

                    (PREDICATE HEADER MATCH)

               evaluates to non-‘nil’.  For instance, the advanced match
               ‘("lines" 4 <)’ (*note Advanced Scoring::) will result in
               the following form:

                    (< header-value 4)

               Or to put it another way: When using ‘<’ on ‘Lines’ with
               4 as the match, we get the score added if the article has
               less than 4 lines.  (It’s easy to get confused and think
               it’s the other way around.  But it’s not.  I think.)

               When matching on ‘Lines’, be careful because some back
               ends (like ‘nndir’) do not generate ‘Lines’ header, so
               every article ends up being marked as having 0 lines.
               This can lead to strange results if you happen to lower
               score of the articles with few lines.

          “Date”
               For the Date header we have three kinda silly match
               types: ‘before’, ‘at’ and ‘after’.  I can’t really
               imagine this ever being useful, but, like, it would feel
               kinda silly not to provide this function.  Just in case.
               You never know.  Better safe than sorry.  Once burnt,
               twice shy.  Don’t judge a book by its cover.  Never not
               have sex on a first date.  (I have been told that at
               least one person, and I quote, “found this function
               indispensable”, however.)

               A more useful match type is ‘regexp’.  With it, you can
               match the date string using a regular expression.  The
               date is normalized to ISO8601 compact format
               first—YYYYMMDD‘T’HHMMSS.  If you want to match all
               articles that have been posted on April 1st in every
               year, you could use ‘....0401.........’ as a match
               string, for instance.  (Note that the date is kept in its
               original time zone, so this will match articles that were
               posted when it was April 1st where the article was posted
               from.  Time zones are such wholesome fun for the whole
               family, eh?)

               Finally, two actually useful match types for dates: ‘<’
               and ‘>’.  These will allow scoring on the relative age
               (in days) of the articles.  Here’s an example score file
               using the method:

                    (("date"
                      (7 10 nil <)
                      (7 -10 nil >)
                      (14 -10 nil >)))

               This results in articles less than a week old getting a
               10 point increase, articles older than a week getting a
               10 point decrease, and articles older than two weeks
               getting a cumulative 20 point decrease.

               The day can also be a floating point number: To score
               articles less than an hour old, you can say ‘(0.04 10 nil
               <)’.

          “Head, Body, All”
               These three match keys use the same match types as the
               ‘From’ (etc.) header uses.

          “Followup”
               This match key is somewhat special, in that it will match
               the ‘From’ header, and affect the score of not only the
               matching articles, but also all followups to the matching
               articles.  This allows you to increase the score of
               followups to your own articles, or decrease the score of
               followups to the articles of some known trouble-maker.
               Uses the same match types as the ‘From’ header uses.
               (Using this match key will lead to creation of ‘ADAPT’
               files.)

          “Thread”
               This match key works along the same lines as the
               ‘Followup’ match key.  If you say that you want to score
               on a (sub-)thread started by an article with a
               ‘Message-ID’ X, then you add a ‘thread’ match.  This will
               add a new ‘thread’ match for each article that has X in
               its ‘References’ header.  (These new ‘thread’ matches
               will use the ‘Message-ID’s of these matching articles.)
               This will ensure that you can raise/lower the score of an
               entire thread, even though some articles in the thread
               may not have complete ‘References’ headers.  Note that
               using this may lead to nondeterministic scores of the
               articles in the thread.  (Using this match key will lead
               to creation of ‘ADAPT’ files.)

‘score-fn’
     The value of this entry should be one or more user-defined function
     names in parentheses.  Each function will be called in order and
     the returned value is required to be an integer.

          (score-fn (custom-scoring))

     The user-defined function is called with an association list with
     the keys ‘number subject from date id refs chars lines xref extra’
     followed by the article’s score before the function is run.

     The following (somewhat contrived) example shows how to use a
     user-defined function that increases an article’s score by 10 if
     the year of the article’s date is also mentioned in its subject.

          (defun custom-scoring (article-alist score)
            (let ((subject (cdr (assoc 'subject article-alist)))
                  (date (cdr (assoc 'date article-alist))))
              (if (string-match (number-to-string
                                 (nth 5 (parse-time-string date)))
                                subject)
                  10)))

     ‘score-fn’ entries are permanent and can only be added or modified
     directly in the ‘SCORE’ file.

‘mark’
     The value of this entry should be a number.  Any articles with a
     score lower than this number will be marked as read.

‘expunge’
     The value of this entry should be a number.  Any articles with a
     score lower than this number will be removed from the summary
     buffer.

‘mark-and-expunge’
     The value of this entry should be a number.  Any articles with a
     score lower than this number will be marked as read and removed
     from the summary buffer.

‘thread-mark-and-expunge’
     The value of this entry should be a number.  All articles that
     belong to a thread that has a total score below this number will be
     marked as read and removed from the summary buffer.
     ‘gnus-thread-score-function’ says how to compute the total score
     for a thread.

‘files’
     The value of this entry should be any number of file names.  These
     files are assumed to be score files as well, and will be loaded the
     same way this one was.

‘exclude-files’
     The clue of this entry should be any number of files.  These files
     will not be loaded, even though they would normally be so, for some
     reason or other.

‘eval’
     The value of this entry will be ‘eval’ed.  This element will be
     ignored when handling global score files.

‘read-only’
     Read-only score files will not be updated or saved.  Global score
     files should feature this atom (*note Global Score Files::).
     (Note: “Global” here really means “global”; not your personal
     apply-to-all-groups score files.)

‘orphan’
     The value of this entry should be a number.  Articles that do not
     have parents will get this number added to their scores.  Imagine
     you follow some high-volume newsgroup, like ‘comp.lang.c’.  Most
     likely you will only follow a few of the threads, also want to see
     any new threads.

     You can do this with the following two score file entries:

                  (orphan -500)
                  (mark-and-expunge -100)

     When you enter the group the first time, you will only see the new
     threads.  You then raise the score of the threads that you find
     interesting (with ‘I T’ or ‘I S’), and ignore (‘c y’) the rest.
     Next time you enter the group, you will see new articles in the
     interesting threads, plus any new threads.

     I.e., the orphan score atom is for high-volume groups where a few
     interesting threads which can’t be found automatically by ordinary
     scoring rules exist.

‘adapt’
     This entry controls the adaptive scoring.  If it is ‘t’, the
     default adaptive scoring rules will be used.  If it is ‘ignore’, no
     adaptive scoring will be performed on this group.  If it is a list,
     this list will be used as the adaptive scoring rules.  If it isn’t
     present, or is something other than ‘t’ or ‘ignore’, the default
     adaptive scoring rules will be used.  If you want to use adaptive
     scoring on most groups, you’d set ‘gnus-use-adaptive-scoring’ to
     ‘t’, and insert an ‘(adapt ignore)’ in the groups where you do not
     want adaptive scoring.  If you only want adaptive scoring in a few
     groups, you’d set ‘gnus-use-adaptive-scoring’ to ‘nil’, and insert
     ‘(adapt t)’ in the score files of the groups where you want it.

‘adapt-file’
     All adaptive score entries will go to the file named by this entry.
     It will also be applied when entering the group.  This atom might
     be handy if you want to adapt on several groups at once, using the
     same adaptive file for a number of groups.

‘local’
     The value of this entry should be a list of ‘(VAR VALUE)’ pairs.
     Each VAR will be made buffer-local to the current summary buffer,
     and set to the value specified.  This is a convenient, if somewhat
     strange, way of setting variables in some groups if you don’t like
     hooks much.  Note that the VALUE won’t be evaluated.