On 16.11.2017 20:51, Andreas Röhler wrote:
> Feature request:
>
> Currently variable kill-do-not-save-duplicates checks only the (car 
> kill-ring) as docu explains:
>
> Do not add a new string to ‘kill-ring’ if it duplicates the last one.
> The comparison is done using ‘equal-including-properties’.
>
> AFAIU it would be trivial replace this check by a call of "member", 
> thus checking the whole kill-ring.
>
> Thanks,
>
> Andreas
>
>

This variant of kill-new should do it. Diff basically at comment " ;; 
delete string from kill-ring"

(defun ar-kill-new (string &optional replace)
   "Make STRING the latest kill in the kill ring.
Set `kill-ring-yank-pointer' to point to it.
If `interprogram-cut-function' is non-nil, apply it to STRING.
Optional second argument REPLACE non-nil means that STRING will replace
the front of the kill ring, rather than being added to the list.

When `save-interprogram-paste-before-kill' and `interprogram-paste-function'
are non-nil, saves the interprogram paste string(s) into `kill-ring' before
STRING.

When the yank handler has a non-nil PARAM element, the original STRING
argument is not used by `insert-for-yank'.  However, since Lisp code
may access and use elements from the kill ring directly, the STRING
argument should still be a \"useful\" string for such uses."
   (let (newring)
     (unless (and kill-do-not-save-duplicates
                  ;; Due to text properties such as 'yank-handler that
                  ;; can alter the contents to yank, comparison using
                  ;; `equal' is unsafe.
                  (equal-including-properties string (car kill-ring)))
       (if (fboundp 'menu-bar-update-yank-menu)
           (menu-bar-update-yank-menu string (and replace (car 
kill-ring)))))
     (when save-interprogram-paste-before-kill
       (let ((interprogram-paste (and interprogram-paste-function
                                      (funcall 
interprogram-paste-function))))
         (when interprogram-paste
           (dolist (s (if (listp interprogram-paste)
                          (nreverse interprogram-paste)
                        (list interprogram-paste)))
             (unless (and kill-do-not-save-duplicates
                          (equal-including-properties s (car kill-ring)))
               (push s kill-ring))))))
     (if (and kill-do-not-save-duplicates
          (member string kill-ring))
     (progn
       ;; delete string from kill-ring
       (dolist (ele kill-ring)
         (unless (equal-including-properties string ele)
           (push ele newring)))
       ;; push the match at top
       (push string newring)
       (setq kill-ring newring))
       (if (and replace kill-ring)
           (setcar kill-ring string)
         (push string kill-ring)
         (if (> (length kill-ring) kill-ring-max)
             (setcdr (nthcdr (1- kill-ring-max) kill-ring) nil))))
     (setq kill-ring-yank-pointer kill-ring)
     (if interprogram-cut-function
         (funcall interprogram-cut-function string))))