bug#28466: 26.0.50; diff in vc-outgoing doesn't work properly

[Tom Tromey]

I'm using vc-dir mode.
I used "O" to show the outgoing changes.

In the *vc-outgoing* buffer, I selected the entire buffer
(C-x h) and then typed "=" to make a diff.

I was expecting to see a diff showing the combined contents of all 3 of
my outgoing patches.

However, the generated diff is missing the oldest patch in the series.

Tom



In GNU Emacs 26.0.50 (build 20, x86_64-pc-linux-gnu, GTK+ Version 3.22.17)
 of 2017-09-14 built on bapiya
Repository revision: a7036e04014e5b0548653f26f87ee9e98be05ba3
Windowing system distributor 'Fedora Project', version 11.0.11903000
System Description:     Fedora release 25 (Twenty Five)

Recent messages:
Mark set
Quit [3 times]
Mark activated
next-line: End of buffer
Finding changes in ....
Quit [2 times]
next-line: End of buffer
Mark set
previous-line: Beginning of buffer
Finding changes in ....
scroll-up-command: End of buffer
Configured using:
 'configure --prefix=/home/tromey/Emacs/install'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 LCMS2

Important settings:
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: @im=ibus
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Major mode: Diff

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  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
/home/tromey/.emacs.d/elpa/bubbles-0.5/bubbles hides 
/home/tromey/Emacs/install/share/emacs/26.0.50/lisp/play/bubbles

Features:
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Memory information:
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 (strings 32 518815 50035)
 (string-bytes 1 13923769)
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