bug#24089: 25.1; Dired: diff error on = <RET> if the file has a backup inside .~/

[Jorge Peixoto de Morais Neto]

Please extract the attached gzipped tarball into ~.

Inside ~, start Emacs with an init file containing the following:
--8<---------------cut here---------------start------------->8---
(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(backup-directory-alist (quote (("." . ".~"))))
)

(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 )
--8<---------------cut here---------------end--------------->8---

Perform the following steps:
1. C-x d ~/dired-diff-bug-1 <RET>
2. j dummy <RET>
3. = <RET>
I expected (according to the documentation of dired-diff) to see the
diff of dummy with its backup.  Instead a diff error occurs.  I have
saved the diff error buffer to diff-error-dummy.txt and attached it.

Now perform the following steps:
1. C-x d ~/dired-diff-bug-1/.~ <RET>
2. j dummy~ <RET>
3. = <RET>.
A similar diff error occurs. It is also unexpected.  I have saved the
diff error buffer in diff-error-dummy~.txt and attached it.

I have also attached a dribble file.

report-emacs-bug was invoked from another Emacs session, also invoked with an
init file having the contents specified above.


In GNU Emacs 25.1.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.9)
 of 2016-07-25 built on jorge-HP-G42
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description:     Ubuntu 16.04.1 LTS

Configured using:
 'configure --prefix=/usr/local/emacs/ --with-modules'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES

Important settings:
  value of $LC_MONETARY: en_DK.UTF-8
  value of $LC_NUMERIC: en_DK.UTF-8
  value of $LC_TIME: en_DK.UTF-8
  value of $LANG: 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
  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
  blink-cursor-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 messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

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Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec password-cache epg gnus-util mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
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Memory information:
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dired-diff-bug-1.tar.gz
Description: application/compressed-tar

diff-error-dummy.txt
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diff-error-dummy~.txt
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dribble.txt
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