bug#15980: 24.3.50; `minibuffer-complete-word': case where it does not work correctly

[Drew Adams <drew.adams@oracle.com>]

Seems like the behavior is wrong in this case, but I see that the same
behavior is found for Emacs 20 through 24.  So I cannot say for sure
whether this is a bug.  At least the behavior does not seem to follow
the doc.

The doc ((emacs) `Completion Commands') says that SPC does this:

  Complete up to one word from the minibuffer text before point
  (`minibuffer-complete-word').

emacs -Q

(defun cmd\ \ \ \ w\ ith\ spaces () (interactive) (message "SPACES"))

(defun cmd-without-spaces () (interactive) (message "NOPE"))

M-x cm SPC ; correctly completes to `cmd'
SPC        ; completes to `cmd '

Since SPC is supposed to complete a word at a time, and since both ` '
and `-' are word separators, I would expect that there are two
word completions for the prefix `cmd': `cmd ' and `cmd-'.

So I would expect to see *Completions* displayed, showing the two
candidates `cmd    w ith spaces' and `cmd-without-spaces'.

Admittedly, this is a corner use case.


In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-11-20 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'