Handle help-form in y-or-n-p and use this in find-file-noselect (bug#5423)

* doc/lispref/help.texi (Help Functions): Mention help-form for
read-char-from-minibuffer and y-or-n-p.

* doc/lispref/minibuf.texi (Yes-or-No Queries): Mention help-form
for y-or-n-p.
(Multiple Queries): Mention help-form for read-char-from-minibuffer.

* lisp/files.el (find-file-noselect): Let-bind multi-line help text
to help-form for y-or-n-p.

* lisp/subr.el (read-char-choice): Mention help-form in docstring.
(read-char-from-minibuffer): Mention help-form in docstring.
(y-or-n-p-map): Remove handling of 'help'.
(y-or-n-p): Mention help-form in docstring.
When help-form is non-nil: add help-char to 'prompt', and bind
help-char to help-form-show in composed-keymap.

1 files changed, 3 insertions, 2 deletions

diff --git a/doc/lispref/help.texi b/doc/lispref/help.texi
index 2fa54e3b66b..90406df9c19 100644
--- a/doc/lispref/help.texi
+++ b/doc/lispref/help.texi
@@ -676,8 +676,9 @@ If this variable is non-@code{nil}, its value is a form to evaluate
 whenever the character @code{help-char} is read.  If evaluating the form
 produces a string, that string is displayed.
 
-A command that calls @code{read-event}, @code{read-char-choice}, or
-@code{read-char} probably should bind @code{help-form} to a
+A command that calls @code{read-event}, @code{read-char-choice},
+@code{read-char}, @code{read-char-from-minibuffer}, or
+@code{y-or-n-p} probably should bind @code{help-form} to a
 non-@code{nil} expression while it does input.  (The time when you
 should not do this is when @kbd{C-h} has some other meaning.)
 Evaluating this expression should result in a string that explains