bug#50414: 27.2; gnus-group-default-list-level documentation wrong

[Allen Li]

The documentation for gnus-group-default-list-level states:

  Default listing level.
  Ignored if ‘gnus-group-use-permanent-levels’ is non-nil.

This does not appear to be entirely true:

  (defun gnus-group-default-level (&optional level number-or-nil)
    (cond
     (gnus-group-use-permanent-levels
      (or (setq gnus-group-use-permanent-levels
                (or level (if (numberp gnus-group-use-permanent-levels)
                              gnus-group-use-permanent-levels
                            (or (gnus-group-default-list-level)
                                gnus-level-subscribed))))
          (gnus-group-default-list-level) gnus-level-subscribed))
     (number-or-nil
      level)
     (t
      (or level (gnus-group-default-list-level) gnus-level-subscribed))))

When gnus-group-use-permanent-levels is first set (to t via customize), the 
default
level still depends on gnus-group-default-list-level.  After that
however, the level will indeed be based off of
gnus-group-use-permanent-levels which will be set to a number.

Might I suggest:

  Default listing level.
  When ‘gnus-group-use-permanent-levels’ is non-nil, this level is
  used as the starting level until the user sets a different level.

In GNU Emacs 27.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.27, cairo 
version 1.17.4)
 of 2021-03-26 built on juergen
Windowing system distributor 'The X.Org Foundation', version 11.0.12013000
System Description: Arch Linux