bug#39353: [PATCH] Use current-prefix-arg instead of prefix-arg

[Kyle Hubert <khubert@gmail.com>]

Forwarding arguments through to children function invocations should
be handled by current-prefix-arg. This was first uncovered when ediff
used full window width scrolling in ediff-scroll-horizontally, when
the call to scroll-left or scroll-right should have been half-window
size. Through further grepping, there was another usage in
simple.el. Note, execute-extended-command was visually inspected that
it was in interactive mode.

---
 lisp/simple.el        | 2 +-
 lisp/vc/ediff-util.el | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/lisp/simple.el b/lisp/simple.el
index 2ec3da680f..53afa7b138 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1888,7 +1888,7 @@ invoking, give a prefix argument to `execute-extended-command'."
     ;; `function' and not `execute-extended-command'.  The difference is
     ;; visible in cases such as M-x <cmd> RET and then C-x z (bug#11506).
     (setq real-this-command function)
-    (let ((prefix-arg prefixarg))
+    (let ((current-prefix-arg prefixarg))
       (command-execute function 'record))
     ;; If enabled, show which key runs this command.
     ;; But first wait, and skip the message if there is input.
diff --git a/lisp/vc/ediff-util.el b/lisp/vc/ediff-util.el
index a8af9ba37a..5f8a4a86b1 100644
--- a/lisp/vc/ediff-util.el
+++ b/lisp/vc/ediff-util.el
@@ -1540,10 +1540,10 @@ the width of the A/B/C windows."
    ;; hscrolling.
    (if (= last-command-event ?<)
        (lambda (arg)
-	 (let ((prefix-arg arg))
+	 (let ((current-prefix-arg arg))
 	   (call-interactively #'scroll-left)))
      (lambda (arg)
-       (let ((prefix-arg arg))
+       (let ((current-prefix-arg arg))
 	 (call-interactively #'scroll-right))))
    ;; calculate argument to scroll-left/right
    ;; if there is an explicit argument
-- 
2.25.0