bug#60897: 29.0.60; vc-revert fails to revert buffer

[Eric Gillespie <epg@pretzelnet.org>]

1. git clone git://git.sv.gnu.org/emacs.git
2. emacs -Q emacs/BUGS
3. Make any change at all.  Save it.
4. C-x v =
5. C-x v u

Step 4 switches to the diff buffer, as it always has (good).

If you switch back to the file buffer and C-x v u there, the file
is reverted and with it the buffer.

But we're staying in the diff buffer:

Expected behavior:
File and buffer both reverted.

Actual behavior:
File is reverted but buffer is NOT.


bisect results:

4803fba487d41f0817feab48b5095ef4b4940ff6 is the first bad commit
commit 4803fba487d41f0817feab48b5095ef4b4940ff6
Author: Juri Linkov <juri@linkov.net>
Date:   Sun Aug 28 22:38:51 2022 +0300

    'C-x v v' on a diff buffer commits it as a patch (bug#52349)



In GNU Emacs 29.0.60 (build 4, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.16.0) of 2023-01-17 built on dogato
Repository revision: 56d69c2fc4782dc23bd79ddcbccfbae9b263ecac
Repository branch: emacs-29
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: openSUSE Leap 15.4

Configured using:
 'configure -C --prefix=/home/epg/.local --disable-silent-rules
 --without-libsystemd --without-xft --without-m17n-flt
 --without-toolkit-scroll-bars --without-gpm --without-dbus
 --without-gsettings --without-selinux --without-compress-install
 --without-tree-sitter --with-x CC=gcc-11'

Configured features:
CAIRO FREETYPE GIF GLIB GMP GNUTLS HARFBUZZ JPEG JSON LIBXML2 MODULES
NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF WEBP
X11 XDBE XIM XINPUT2 XPM LUCID ZLIB

Important settings:
  value of $LC_CTYPE: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny rfc822
mml mml-sec password-cache epa derived epg rfc6068 epg-config gnus-util
text-property-search time-date subr-x mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils vc-hg vc-bzr vc-src
vc-sccs vc-svn vc-cvs vc-rcs log-view pcvs-util smerge-mode diff
whitespace vc vc-git diff-mode easy-mmode vc-dispatcher dired-aux
cl-loaddefs cl-lib dired dired-loaddefs rmc iso-transl tooltip cconv
eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type
elisp-mode mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd
fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow
isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads inotify dynamic-setting
font-render-setting cairo x-toolkit xinput2 x multi-tty
make-network-process emacs)

Memory information:
((conses 16 55463 8329)
 (symbols 48 6885 0)
 (strings 32 21222 2121)
 (string-bytes 1 592863)
 (vectors 16 13020)
 (vector-slots 8 183606 11153)
 (floats 8 27 40)
 (intervals 56 545 0)
 (buffers 976 17))