Fix purcell#26

Calling `put-text-property` on the return value of
`filter-buffer-substring-function` will result in modifying
`buffer-undo-list`, which is bad.  We use `propertize` instead in
order to add text properties without modifying the original string.

whole-line-or-region-test.el

@@ -509,6 +509,29 @@ third"
 second
 third")))
 
+(ert-deftest wlr-regression-issue-26 ()
+  (wlr-before-after
+   "CREATE TABLE account (
+  name VARCHAR(10) NOT NULL
+);|"
+   (buffer-enable-undo)
+   (transient-mark-mode 1)
+   (goto-line 2)
+   (call-interactively 'whole-line-or-region-kill-region)
+   "CREATE TABLE account (
+|);"
+   (primitive-undo 1 buffer-undo-list)
+   "CREATE TABLE account (
+|  name VARCHAR(10) NOT NULL
+);"
+   (search-forward "10")
+   (set-mark (- (point) 2))
+   (should (region-active-p))
+   (call-interactively 'whole-line-or-region-kill-ring-save)
+   (call-interactively 'yank)
+   "CREATE TABLE account (
+  name VARCHAR(1010|) NOT NULL
+);"))
 
 
 (provide 'whole-line-or-region-test)

whole-line-or-region.el

@@ -173,11 +173,9 @@ The binding ensure killed strings have a yank handler attached."
     `(let* ((,orig filter-buffer-substring-function)
             (filter-buffer-substring-function
              (lambda (&rest args)
-               (let ((s (apply ,orig args)))
-                 (put-text-property 0 (length s) 'yank-handler
-                                    '(whole-line-or-region-yank-handler nil t)
-                                    s)
-                 s))))
+               (propertize (apply ,orig args)
+                           'yank-handler
+                           '(whole-line-or-region-yank-handler nil t)))))
        ,@body)))
 
 (defun whole-line-or-region-wrap-region-kill (f num-lines)