bug#15381: 24.3; NTEmacs write-region behaviour with MUSTBENEW set to 'excl

[Phil Sainty <psainty@orcon.net.nz>]

I'm using write-region with the MUSTBENEW argument set to 'excl
to prohibit writing to an existing file. This works as advertised
on Ubuntu, but I happened to try the code under Windows and found
that the write was not prevented.

I further observed that, in this circumstance, the written
content only overwrites the start of the target file (leaving
the remainder), rather than replacing the whole file. This
appears to be the same behaviour as setting the APPEND argument
to zero.

Setting MUSTBENEW to t works as expected.

I'm using the following to test:

M-: (write-region (region-beginning) (region-end) "~/somefile" nil nil 
nil 'excl) RET





In GNU Emacs 24.3.1 (i386-mingw-nt5.1.2600)
  of 2013-03-18 on MARVIN
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
  `configure --with-gcc (4.7) --cflags
  -ID:/devel/emacs/libs/libXpm-3.5.8/include
  -ID:/devel/emacs/libs/libXpm-3.5.8/src
  -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
  -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
  -ID:/devel/emacs/libs/giflib-4.1.4-1/include
  -ID:/devel/emacs/libs/jpeg-6b-4/include
  -ID:/devel/emacs/libs/tiff-3.8.2-1/include
  -ID:/devel/emacs/libs/gnutls-3.0.9/include
  -ID:/devel/emacs/libs/libiconv-1.13.1-1-dev/include
  -ID:/devel/emacs/libs/libxml2-2.7.8/include/libxml2'

Important settings:
   value of $LANG: ENZ
   locale-coding-system: cp1252
   default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
   tooltip-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   line-number-mode: t
   transient-mark-mode: t

Recent input:
<help-echo> M-x r e p o r t <tab> <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
call-interactively: End of buffer

Load-path shadows:
None found.

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