RE: proposal - minibuffer completion functions

[Drew Adams]

> > 2. Funcall the value of a global variable: `completing-read-fn' or
> >    `read-file-name-fn', if non-nil, to perform the completion. 
> >    Else call a default completing function,
> >    `completing-read-default' or `read-file-name-default'.
> 
> We have already `read-file-name-function', `read-buffer-function',
> but I can't find the same for `completing-read'.

Thank you, Juri. This is great news. I wasn't aware of `read-file-name-function'
(new with Emacs 22, apparently). 

There is apparently no `read-file-name-default', but the same effect can be had
by binding `read-file-name-function' to nil.

So now all we need is `completing-read-function'.