bug#18694: 25.0.50; `ibuffer(-saved)-filter-groups', `ibuffer-saved-filters'

[Drew Adams]

As introduction, here is one user's attempt to understand the structure
of `ibuffer-saved-filter-groups':
http://emacs.stackexchange.com/q/2087/105

The user says: "I'm guessing at the predicate bit as I can't find any
examples or documentation. What should it really look like?"

1. The doc string for these variables should describe the structure
better.  It should not send readers off to look at the doc string of
internal variable `ibuffer-filtering-qualifiers', especially since that
doc string just says that a qualifier has the form (SYMBOL . QUALIFIER),
and it does not even say what form or type this QUALIFIER has as a Lisp
entity.

This would also encourage you not to use QUALIFIER in two completely
different ways: QUALIFIER ==> (SYMBOL . QUALIFIER).

The doc of the two user options even refers to the doc string of
`ibuffer-filtering-qualifiers' *twice*, unnecessarily.

2. The defcustoms of the user options should use something more specific
(so more useful to users) as the :type than just (repeat 'sexp).  A
better :type will help users customize the option and understand its
structure.  And if you try to specify the structure for defcustom :type
then maybe that will help you do a better job of describing it for
users in the doc string.


In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2014-10-06 on LEG570
Bzr revision: 118063 monnier@iro.umontreal.ca-20141006174756-y7ha091r491l1ijw
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 CPPFLAGS=-DGLYPH_DEBUG=1'