(undo-more): Add comment explaining the operations on pending-undo-list

and buffer-undo-list.

1 files changed, 3 insertions, 0 deletions

diff --git a/lisp/simple.el b/lisp/simple.el
index 7cd321564d9..6ebbd71cdbf 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1725,6 +1725,9 @@ then call `undo-more' one or more times to undo them."
       (error (concat "No further undo information"
                      (and undo-in-region " for region"))))
   (let ((undo-in-progress t))
+    ;; Note: The following, while pulling elements off
+    ;; `pending-undo-list' will call primitive change functions which
+    ;; will push more elements onto `buffer-undo-list'.
     (setq pending-undo-list (primitive-undo n pending-undo-list))
     (if (null pending-undo-list)
         (setq pending-undo-list t))))