making ~/News/nnrss:* filenames utf-8

[jidanni]

How do I clean up mule-utf-8 filenames? (guaranteed to give garbage
characters for non-ASCII to anybody who looks at them, made even when
RSS is UTF-8 already.)

$ ls News/nnrss:*|iconv>/dev/null
iconv: illegal input sequence at position 19

In (info "(gnus)RSS") it says
     The `nnrss' back end saves the group data file in `nnrss-directory'
  (see below) for each `nnrss' group.  File names containing non-ASCII
  characters will be encoded by the coding system specified with the
  `nnmail-pathname-coding-system' variable.  If it is `nil', in Emacs the
  coding system defaults to the value of
  `default-file-name-coding-system'.
Which says:
  default-file-name-coding-system is a variable defined in `C source code'.
  Its value is mule-utf-8
  This variable is set/changed by the command `set-language-environment'.
  User should not set this variable manually,
  instead use `file-name-coding-system' to get a constant encoding
  of file names regardless of the current language environment.

So how does one change those filenames to UTF-8 safely?
$ for i in nnrss:*; do mv $i `echo $i|WHAT`; done
then echo "(setq file-name-coding-system 'utf-8)">> .emacs
then start emacs?
I use Debian unstable, emacs-version "22.2.1".
Yes, I hear emacs 23 is UTF-8 already.

P.S., Ding list broken:
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