bug#25482: 26.0.50; Allow setting `query-replace-from-to-separator` to nil

[Eli Zaretskii]

> From: Thierry Volpiatto <thierry.volpiatto@gmail.com>
> Cc: 25482@debbugs.gnu.org
> Date: Fri, 20 Jan 2017 12:35:29 +0100
> 
> With actual code:
> 
> 1) Using (setq query-replace-from-to-separator " -> ")
> is not working.
> 
> 2) Using (customize-set-variable query-replace-from-to-separator " -> ")
> is working but " -> " will not be a plain ascii string and will be added
> to history.
> 
> 3) Setting query-replace-from-to-separator to nil is not possible, apart 
> perhaps
> using a sexp that evaluate to nil, which is not obvious and in which
> case do not add a prompt with a default value like in 24.5 (regression).
> 
> With the patch:
> 
> 1) and 2) are working and preserve the actual behavior, which is adding
> "from<separator>to" to history.
> 
> 3) Is working and provide the exact behavior as 24.5, that is use a
> plain ascii string " -> " as separator and do not add
> "from<separator>to" to history.
> 
> The default setting is the same as the actual code, no change.

Yes, I understand.

I'm asking whether the (fixed) behavior, whereby using setq to change
the value to " -> " would add the ASCII string " -> " to the
minibuffer history, would be acceptable.  If not, please tell why.

Thanks.