bug#39044: 27.0.50; On git log-view-diff does not work for moved files.

[David Koppelman]

With (setq vc-git-print-log-follow t) visit a file in a git repo that
was moved from some other directory and which had changes when in that
other directory. Start log view, C-x v =, move the cursor to a commit
made in the file's former location, and press d (log-view-diff). Rather
than showing a diff, a message reporting no changes is shown.

This flaw was noted in bug 8756, covering vc-diff/log-view, but was
left to a follow on bug.
(https://debbugs.gnu.org/cgi/bugreport.cgi?bug=8756).

Interestingly, vc-annotate has no trouble with renames. See
commit d1e4c4037e88f3256db19813805d03f8ad0291fa.



In GNU Emacs 27.0.50 (build 5, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2019-12-20 built on cyc.ece.lsu.edu
Repository revision: 85a60da92d4db5c87ecfa152501d246425550fc3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Scientific Linux 7.7 (Nitrogen)

Configured using:
 'configure CFLAGS=-O3 --without-pop'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GSETTINGS GLIB NOTIFY INOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS JSON PDUMPER LCMS2
GMP

Important settings:
  value of $LC_COLLATE: C
  value of $LC_TIME: C
  value of $LANG: en_US.utf8
  locale-coding-system: utf-8-unix

Major mode: log

Minor modes in effect:
  shell-dirtrack-mode: t
  global-hi-lock-mode: t
  hi-lock-mode: t
  which-function-mode: t
  flyspell-mode: t
  tooltip-mode: t
  global-eldoc-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
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Features:
(shadow emacsbug smerge-mode diff whitespace bug-reference vc-annotate
log-view pcvs-util vc vc-dispatcher vc-git diff-mode mhtml-mode css-mode
smie eww mm-url url-queue js cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs sgml-mode p-viewer misearch
multi-isearch bbdb-gui flow-fill gnus-uu yenc mailalias smtpmail
sendmail nnir shr-color color sort gnus-cite smiley mm-archive
gnus-async gnus-bcklg qp cl-extra gnus-ml disp-table gnus-topic utf-7
gnutls network-stream nsm imap rfc2104 nndoc nndraft nnmh nnmbox
bbdb-gnus bbdb-snarf mail-extr bbdb-com gnus-agent gnus-srvr gnus-score
score-mode nnvirtual gnus-msg gnus-art mm-uu mml2015 mm-view mml-smime
smime dig nntp gnus-cache gnus-sum url url-proxy url-privacy url-expand
url-methods url-history mailcap shr url-cookie url-domsuf url-util svg
xml dom gnus-group gnus-undo gnus-start gnus-cloud nnimap nnmail
mail-source utf7 netrc nnoo parse-time iso8601 gnus-spec gnus-int
gnus-range gnus-win gnus nnheader wid-edit add-log help-mode mule-util
cal-move p-iimage easy-mmode simtools p-tex-funcs shell pcomplete comint
ring man ansi-color hi-lock p-stop-time time-stamp dired-aux p-page
dabbrev ps-print ps-print-loaddefs ps-def lpr holidays hol-loaddefs appt
p-diary-aux cal-x p-diary-audit diary-lib diary-loaddefs cal-menu
calendar cal-loaddefs paren mic-paren message rmc puny dired
dired-loaddefs format-spec rfc822 mml mml-sec epa epg epg-config
gnus-util rmail rmail-loaddefs text-property-search time-date mm-decode
mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 mm-util
ietf-drums mail-prsvr mailabbrev mail-utils gmm-utils mailheader ffap
thingatpt ccl-mode ampl-mode bbdb-autoloads bbdb timezone texize
chemora-mode which-func imenu flyspell ispell gnuplot-mode edmacro
kmacro p-autoreload derived sd image-file advice package easymenu
browse-url url-handlers url-parse auth-source cl-seq eieio eieio-core
cl-macs eieio-loaddefs password-cache json subr-x map url-vars seq
byte-opt gv bytecomp byte-compile cconv cl-loaddefs cl-lib tooltip eldoc
electric uniquify ediff-hook vc-hooks lisp-float-type 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 elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic 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 charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded 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 threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 321268 49388)
 (symbols 48 28911 1)
 (strings 32 92367 7980)
 (string-bytes 1 3634829)
 (vectors 16 47078)
 (vector-slots 8 1360945 151650)
 (floats 8 775 1958)
 (intervals 56 11966 7520)
 (buffers 1000 79)
 (heap 1024 59319 13646))