Git bisected the Emacs repo at Savannah to:
046fb9fbdc0ee0c26e0063ce5ee94bead46ee98d is the first bad commit
commit 046fb9fbdc0ee0c26e0063ce5ee94bead46ee98d
Author: Dmitry Antipov <dmantipov@yandex.ru>
Date: Tue Dec 11 13:51:12 2012 +0400
* buffer.c (Fset_buffer_multibyte): Do not force redisplay
if changed buffer is not shown in a window.
* insdel.c (prepare_to_modify_buffer): Likewise.
* window.c (replace_buffer_in_windows_safely): Do nothing
if buffer is not shown in a window.
(Fforce_window_update): Likewise if string or buffer argument
is passed.
:040000 040000 c3cd9f89a3926ca04ecfee03ae667056986ba352 385c925b8bcfcc59262a140e4ce8701b20eb7265 M src