bug#25105: 26.0.50; diff navigation is broken

[Mark Oteiza]

I am guessing this is a consequence of bug#17544. From -Q:

1. Do C-x v d RET = in a repository with a bunch of worktree changes
2. Hit n. Point is now at the top of the SECOND hunk
3. Go to end of buffer.
4. Hit p. Point is now at the top of the PENULTIMATE hunk

Further, from -Q:

1. Find a file generated by git format-patch. I had on hand the v2 patches
from bug#24966.
2. Hit M-n. Emacs complains "Can’t find the beginning of the file"

These are all regressions from Emacs 25.1

In GNU Emacs 26.0.50.1 (x86_64-unknown-linux-gnu, X toolkit, Xaw scroll bars)
 of 2016-12-04 built on logos
Repository revision: 35a86f0b6fe5634e94212964657c538739743d72

Configured using:
 'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --without-gconf --with-modules
 --with-x-toolkit=lucid 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe
 -fstack-protector-strong -g -fvar-tracking-assignments -g
 -fvar-tracking-assignments' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

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

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