bug#19543: 24.4; vc-mode: 'Fileset is up-to-date' even when vc-diff showed differences

[Ed Avis]

Open a file under version control (I used an svn working copy).
Do not make any changes to the file in Emacs, so that the modification
flag remains unset.  But change the file contents outside Emacs,
for example

    M-! echo hello >>foo

Now do C-x v = to show differences.  There are some changes to check in.
Yet when using C-x v v, Emacs reports 'Fileset is up-to-date',
despite the fact that a moment ago vc-diff showed it wasn't.

I understand that Emacs cannot constantly keep track of times when an
edited file might have been changed by some other program.  And that on
trying to edit the buffer, it will warn 'foo changed on disk...'.
However, for me at least, it is quite a common operation to change a
file somehow and then use an existing Emacs buffer to view the
differences and check it in.  Hence it is frustrating that
vc-next-action does nothing.

If the last vc-diff operation on a file showed changes, then
vc-next-action should revert the buffer contents to what is currently on
disk.  This could even be done without a warning if the modification
flag on the buffer is currently unset and the buffer was under version
control when loaded.  Then a further vc-next-action should commit.



In GNU Emacs 24.4.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.10.9)
 of 2014-11-03 on wcl-linux04.wcl.local
Configured using:
 `configure --build=x86_64-redhat-linux-gnu
 --host=x86_64-redhat-linux-gnu --program-prefix=
 --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
 --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
 --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
 --libexecdir=/usr/libexec --localstatedir=/var
 --sharedstatedir=/var/lib --mandir=/usr/share/man
 --infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
 --with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
 --with-gpm=no build_alias=x86_64-redhat-linux-gnu
 host_alias=x86_64-redhat-linux-gnu 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g
 -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
 -fstack-protector-strong --param=ssp-buffer-size=4
 -grecord-gcc-switches -m64 -mtune=generic' 'LDFLAGS=-Wl,-z,relro ''

Important settings:
  value of $LC_COLLATE: C
  value of $LC_CTYPE: en_GB.UTF-8
  value of $LC_MESSAGES: en_GB.UTF-8
  value of $LC_MONETARY: en_GB.UTF-8
  value of $LC_NUMERIC: en_GB.UTF-8
  value of $LC_TIME: en_GB.UTF-8
  value of $LANG: en_GB.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Diff

Minor modes in effect:
  diff-auto-refine-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-w C-x C-s ESC < C-x k RET C-x 
C-g q C-x v u y e s RET ESC ! p a t c h SPC b u TAB 
SPC < d RET ESC ! v p SPC b u DEL DEL DEL DEL DEL DEL 
DEL c p SPC b u TAB SPC ~ / w i TAB s c TAB RET C-x 
v = C-x o C-s i n t e r e s t r a t e 1 m o f f C-s 
C-s C-s C-s C-s C-a ESC > C-r C-r C-r C-r C-r C-r C-r 
C-a C-x v = ESC [ 6 ~ ESC [ 5 ~ C-x v v C-g C-x v = 
C-x v v C-x o ESC x r e p o r t SPC e m a C-g C-g C-x 
C-f DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL 
DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL 
DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL 
DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL DEL 
DEL DEL j o b RET ESC ! e c h o SPC h e l l o SPC > 
> j o b RET C-x v = C-x v v ESC x r e p o r t - e m 
a c s - b u g SPC RET

Recent messages:
Mark saved where search started
Finding changes in 
/home/eda/svn_working/repos/wwwroot/WaniSystems/Configuration/MarketSampler/jobs/build.trend.signals.xml...done
Fileset is up-to-date
Quit
Finding changes in 
/home/eda/svn_working/repos/wwwroot/WaniSystems/Configuration/MarketSampler/jobs/build.trend.signals.xml...done
Fileset is up-to-date
Quit [2 times]
(Shell command succeeded with no output)
Finding changes in /home/eda/svn_working/repos/job...done
Fileset is up-to-date

Load-path shadows:
None found.

Features:
(shadow sort emacsbug sendmail sh-script smie executable python json
macros rect ispell network-stream starttls tls mail-extr etags
smerge-mode tabify imenu man ediff-ptch ediff-merg ediff-wind ediff-diff
ediff-mult ediff-help ediff-init ediff-util ediff conf-mode log-view
two-column iso-transl edmacro dabbrev mule-util vc-cvs vc-rcs sql view
kmacro cus-edit wid-edit cus-start cus-load perl-mode ffap thingatpt
url-parse auth-source eieio eieio-core gnus-util password-cache url-vars
help-mode diff-mode vc misearch multi-isearch vc-dispatcher vc-svn
nxml-uchnm rng-xsd xsd-regexp rng-cmpct rng-nxml rng-valid rng-loc
rng-uri rng-parse nxml-parse rng-match rng-dt rng-util rng-pttrn nxml-ns
nxml-mode nxml-outln nxml-rap nxml-util nxml-glyph nxml-enc xmltok
pcmpl-unix dired xterm time-date log-edit easy-mmode message format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mailabbrev mail-utils
gmm-utils mailheader pcvs-util add-log server csharp-mode advice
help-fns byte-opt bytecomp byte-compile cconv cc-langs cc-mode cc-fonts
easymenu cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars
cc-defs zoom-frm frame-cmds frame-fns cl-macs avoid cl gv cl-loaddefs
cl-lib compile shell pcomplete comint ring ansi-color tooltip electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list newcomment lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 1423060 129450)
 (symbols 48 31755 0)
 (miscs 40 814 5691)
 (strings 32 73621 14450)
 (string-bytes 1 3790116)
 (vectors 16 35632)
 (vector-slots 8 1579991 202665)
 (floats 8 689 851)
 (intervals 56 175106 1106)
 (buffers 960 165)
 (heap 1024 100883 14170))

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