bug#2229: 23.0.90; Revisiting a modified mbox file shows incorrect buffer

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the [email protected] mailing list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

Assuming that FOO is an mbox-format file:

  emacs -Q
  C-u M-x rmail RET FOO RET

outside Emacs, type "touch FOO" to modify the file FOO behind Emacs's
back.  Back inside Emacs, type "C-u M-x rmail RET FOO RET" again.
Emacs asks whether to discard edits: answer "yes".  Emacs will say "No
mail." (why?) and you will be presented with the contents of the
buffer that holds the entire message collection, not the buffer
showing a single mail message.

If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
If you would like to further debug the crash, please read the file
d:/gnu/emacs/etc/DEBUG for instructions.


In GNU Emacs 23.0.90.1 (i386-mingw-nt5.1.2600)
 of 2009-02-07 on HOME-C4E4A596F7
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4)'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ENU
  value of $XMODIFIERS: nil
  locale-coding-system: cp1255
  default-enable-multibyte-characters: t

Major mode: RMAIL

Minor modes in effect:
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-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> <help-echo> C-u M-x r m a i l <return> 
~ / d a <tab> m a i l . n e w <return> C-u M-x <up> 
<return> <up> <return> y e s <return> M-x r e p o <tab> 
r <tab> <return>

Recent messages:
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