Fix window-start restoring bug

popwin.el

@@ -487,6 +487,9 @@ window will not be selected."
           (when (popwin:window-deletable-p popwin:popup-window)
             (delete-window popwin:popup-window))
           (popwin:restore-window-outline (car (window-tree)) popwin:window-outline)
+          ;; Call `redisplay' here so `window-start' could be set
+          ;; prior to the point change of the master buffer.
+          (redisplay)
           (when (and (not keep-selected)
                      (window-live-p popwin:selected-window))
             (select-window popwin:selected-window)))

test/popwin-test.el

@@ -398,13 +398,31 @@
 
 (ert-deftest popwin-restore-window-start ()
   (popwin-test:common
-   (insert "foo\nbar\n")
+   (insert (make-string 100 ?\n))
    (set-window-start nil (point-max))
    (popwin:popup-buffer buf2)
+   (set-window-start (get-buffer-window buf1) (point-min))
    (popwin:close-popup-window)
    (should (eq (current-buffer) buf1))
    (should (eq (window-start) (point-max)))))
 
+(ert-deftest popwin-restore-window-start/*help* ()
+  (require 'help-mode)
+  (describe-function 'popwin:find-file)
+  (switch-to-buffer (help-buffer))
+  (goto-char (point-min))
+  (should (search-forward "popwin.e" (point-max) t))
+  (call-interactively 'push-button)
+  (goto-char (point-max))
+  (describe-function 'popwin:popup-buffer)
+  (switch-to-buffer (help-buffer))
+  (goto-char (point-min))
+  (should (search-forward "popwin.e" (point-max) t))
+  (call-interactively 'push-button)
+  (sit-for 0)
+  (beginning-of-line)
+  (should (search-forward "popwin:popup-buffer" (line-end-position) t)))
+
 (ert-deftest popwin-original-display-last-buffer ()
   (popwin-test:common
    (popwin:popup-buffer buf2)