bug#54173: 28.0.91; Training wheels for query-replace

[Augusto Stoffel <arstoffel@gmail.com>]

On Sun, 27 Feb 2022 at 08:54, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Augusto Stoffel <arstoffel@gmail.com>
>> Date: Sat, 26 Feb 2022 23:15:12 +0100
>> 
>> I've been using query-replace for years but still seem to have trouble
>> remembering some of the keys.  How about making the help message next to
>> the prompt “(? for help)” customizable, with an option to include an
>> extra summary line?
>
> I don't think it's a good idea to leave documentation and help to
> users.  I'd rather we made the help text better, or maybe introduce a
> key to display a more detailed help text.  Emacs should not have
> sub-optimal help text.

I agree, and I suggested a defcustom here so the user can choose between
two predefined options, the default prompt:

```
Query replacing a with b: (‘?’ for help)
```

and a two-line prompt including a little summary:

```
Query replacing a with b: (‘?’ for help)
Replace ‘y’ once, ‘.’ and exit, ‘!’ all; skip to ‘n’ next, ‘^’ previous; ‘U’ undo all.
```

(The quotation marks are not actually used, they are just representing
the help-key-keybinding face.  I choose this particular message because
it's the best I can fit in 80 columns.)

> Can you tell why you have trouble remembering some of the keys, and
> how changing the help message could countermand that?

My issue is mainly with '.' and '^'.  I rarely need those operations, so
by the time I do I already forgot the keys.  With a summary help line
below the prompt, it's very hard to not be reminded.

PS: Should we define 'p' as a synonym for '^' in 'query-replace-map'?