bug#17375: 24.4.50; minibuffer completion by SPC

[Stefan Monnier <monnier@iro.umontreal.ca>]

> (get-buffer-create "foo-bar")
> That's all!
> Could you try this on `emacs -Q'?  And you will see that the first
> SPC for `C-x b' doesn't insert a space (I'm not quite sure if it
> happens on every platform, though).
> Maybe a buffer-name containing a hyphen triggers this problem.

Indeed, that's it.
It's due to the fix for http://debbugs.gnu.org/15980.

I.e. if we have buffer names " toto" and "foo-bar", then both " " and
"-" have valid completions (remember: C-x b uses substring completion),
so bug#15980 says that instead of choosing arbitrarily between " " and
"-", we should just leave the input unchanged.

I must say I dislike "word completion".  Both because its behavior is
largely ill-defined (e.g. what does it mean to "complete at most
a single word" when the completion table completes "a-b-$FOO-a" to
"a-b-c-a-d-a"?), and because I'd rather leave SPC as a self-insert key.

So in this case, I'd tend to prefer reverting the fix for bug#15980, so
that " " is preferred over "-" on the premise that it makes SPC behave
a bit more like self-insert-command.


        Stefan