Ediff fails on compressed files

[Sven Joachim]

Ediff often fails on compressed files.  Take the following steps to
reproduce it:

$ echo "foo" | gzip -c > foo.gz
$ echo "bar" | gzip -c > bar.gz
$ emacs -Q --eval '(ediff-files "foo.gz" "bar.gz")'

Emacs will beep and display the buffer "*ediff-errors*" containing a
line with

Binary files /tmp/foo.gz and /tmp/bar.gz differ

(or whatever `diff' outputs).

Here is the complete "*Messages*" buffer:

Loading help-fns...done
Loading mwheel...done
(emacs -Q --eval (ediff-files "foo.gz" "bar.gz"))
Loading tool-bar...done
Loading image...done
For information about the GNU Project and its goals, type C-h C-p.
Loading ediff...done
Reading file foo.gz ...
uncompressing foo.gz...done
compressing foo.gz...done
compressing foo.gz...done
Reading file bar.gz ...
uncompressing bar.gz...done
compressing bar.gz...done
compressing bar.gz...done
Computing differences between foo.gz and bar.gz ...
ediff-prepare-error-list: Errors in diff output.  Diff output is in #<buffer 
*ediff-diff*>


In GNU Emacs 22.0.50.1 (i486-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2005-10-29 on debian, modified by Debian
X server distributor `The X.Org Foundation', version 11.0.60802000

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: C
  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: C
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  tool-bar-mode: t
  mouse-wheel-mode: t
  tooltip-mode: t
  auto-compression-mode: t
  menu-bar-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  line-number-mode: t