bug#2962: 23.0.92; tramp. can't copy files plain user -> root (su::/....)

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:

what I did (as a plain user, not root):
1) C-x C-f /su::/usr/src/ (successfully loggen in)
2) C-x C-f /tmp (dired window opened)
3) pressed 'C' on trace.txt file (some arbitrary file):
  -rw-r--r--  1 root    root      96 2009-04-11 00:16 trace.txt
4) then got the message as in *Messages*. Copy process failed of course.
5) just to give more info:
prompt$ ll /tmp/tramp.14050uqL.txt
ls: cannot access /tmp/tramp.14050uqL.txt: No such file or directory

tramp-version is a variable defined in `trampver.el'.
Its value is "2.1.15"

Documentation:
This version of Tramp.

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
/usr/local/share/emacs/23.0.92/etc/DEBUG for instructions.


In GNU Emacs 23.0.92.1 (i686-pc-linux-gnu, GTK+ Version 2.12.12)
 of 2009-04-10 on localhost.localdomain
Windowing system distributor `The X.Org Foundation', version 11.0.10502000
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: en_US.utf8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Dired by name

Minor modes in effect:
  shell-dirtrack-mode: t
  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:
r o l e m <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> c a n ' t SPC c o p y SPC f 
i l e s SPC p a l i n <backspace> <backspace> <backspace> 
<backspace> l a i n SPC u s e r SPC - . <backspace> 
> SPC r o o t SPC ( s u : : / . . . . ) <return> <next> 
<next> <next> <next> <next> <next> <next> <next> <prior> 
<prior> <down> <down> <down> <down> <down> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up> 
<up> <up> <up> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up> 
<up> <up> <up> <up> <up> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <down> <down> <down> 
<down> <down> <down> <down> <down> <up> <up> <up> <up> 
<up> <up> <up> <up> <up> <up> <up> C-c C-k C-g C-c 
C-k C-g C-g C-x k y e s <backspace> <backspace> <backspace> 
y e s <return> <backspace> <backspace> <backspace> 
<return> <down> <down> <down> <down> <down> <escape> 
x C-g C-g <escape> x t m p <return> C-g C-g C-x b t 
m p <return> C <up> <return> <escape> x <up> <retu
rn>

Recent messages:
Copy `/tmp/trace.txt' to `/su:[email protected]:/usr/src/trace.txt' failed:
(file-already-exists File already exists /tmp/tramp.14050uqL.txt)

Mark set
call-interactively: End of buffer [3 times]
Auto-saving...done
Quit [7 times]
Copy `/tmp/trace.txt' to `/su:[email protected]:/usr/src/trace.txt' failed:
(file-already-exists File already exists /tmp/tramp.14050I_X.txt)