bug#35564: [PATCH v4] Tweak dired warning about "wildcard" characters

[Kévin Le Gouguec]

Hello,

I have now added '^' markers below the highlighted command, on condition
that the echo area is wide enough not to wrap lines.

Do we want to add some customizability (highlight face, whether or not
to display '^' markers), or is this good enough for now?


The patch series now includes:

- two patches to make y-or-n-p preserve text properties and implement an
  initial version of highlighting,
- Noam's refactoring patch, plus fixups,
- one patch to add '^' markers,
- one last patch to make tests less tedious to maintain.

0001-Preserve-text-properties-in-y-or-n-p-prompts.patch
Description: Text Data

0002-Tweak-dired-warning-about-wildcard-characters.patch
Description: Text Data

0003-Dedup-dired-aux-isolated-char-searching-Bug-35564.patch
Description: Text Data

0004-fixup-Dedup-dired-aux-isolated-char-searching-Bug-35.patch
Description: Text Data

0005-Add-markers-below-non-isolated-chars-in-dired-prompt.patch
Description: Text Data

0006-Simplify-highlighting-assertions.patch
Description: Text Data

Again, thank you for your patience and your reviews.


PS: the prompt now looks like this ('?' characters are highlighted with
the warning face):

With markers:

> Confirm:
> sed 's/\?/!/'
>         ^
> Send 1 occurrence of ‘?’ as-is to shell?

Without markers:

> Confirm:
> sed 's/\?/!/'
> Send 1 occurrence of ‘?’ as-is to shell?

I added the "Confirm:" line because

- y-or-n-p adds "Please answer y or n.  " before the prompt when the
  user fails to answer correctly, so the markers would not line up if
  the command remained on the first line,

- y-or-n-p adds " (y or n)" after the prompt; I find it more legible to
  have the question next to this suffix, so I did not want to move the
  question to the first line.