bug#12443: 24.2.50; Default values in the minibuffer prompt (fix inconsisntecy)

[Stefan Monnier]

>>> (defcustom minibuffer-default-prompt-format " (default %s)"
>>>  "Default format."
>>>  :type 'string)
>>>
>>> Example of usage:
>>>
>>> (let ((default "def"))
>>>   (read-from-minibuffer
>>>    (format "Set bookmark%s: "
>>>            (format minibuffer-default-prompt-format default))))

Nitpick: `read-from-minibuffer` is a low-level function which you should
never use directly but only within other `read-<foo>` functions.
E.g. here one should probably use `read-string` instead.

Please make sure that `minibuffer-electric-default-mode` pays attention
to it.

> How about taking it even further?   Something along the lines of:
>
>     (format-prompt PROMPT &optional DEFAULT)
>
>     (format-prompt "Set bookmark" default)
>     => "Set bookmark [foobar]: "
>
>     (format-prompt "Goto char")
>     => "Goto char: "

LGTM,


        Stefan