* lisp/isearch.el: C-s C-u M-y reads a string from the kill-ring minibuffer

* lisp/isearch.el: C-s C-u M-y reads a string from the kill-ring minibuffer

* lisp/isearch.el (isearch-yank-from-kill-ring): New command
with code moved from isearch-yank-pop.
(isearch-yank-pop): Use isearch-yank-from-kill-ring.
(isearch-yank-pop-only): Add optional arg, and call
isearch-yank-from-kill-ring when the prefix arg is C-u.
https://lists.gnu.org/archive/html/emacs-devel/2021-01/msg00089.html