dired-undo is misleading

[Martin Schwenke]

I was surprised to see that in GNU Emacs 21.1 and 20.7 (and forever,
according to the lisp/ChangeLog files :-), undo appears to work in a
dired buffer.  Although the documentation for dired-undo says:

  This doesn't recover lost files, it just undoes changes in the
  buffer itself. 

I would be surprised if any user who makes regular use of undo when
editing files would bother to check the documentation for
dired-undo...  until it doesn't do (or undo :-) what they expect!  I
tried it for a laugh and was surprised when it "worked", but then I
hit "g" (revert-buffer) and saw the truth!

Fixes?

* Actually implementing the underlying undo funtionality is too
  difficult without operating system support.

* Have it print a disclaimer in the minibuffer instead of printing the
  comforting string "Undo!", possibly including a suggestion to use
  revert-buffer to see the true state of the directory.  How about:

    Undo!  [Underlying changes were not undone, revert-buffer shows true state!]

* Get rid of dired-undo.  Does anyone actually use it?  It could
  display a message such:

    Too late!  Lucky Emacs users don't make mistakes!

  or

    Insufficient undo information!

  or

    Surely you jest?

Yes, I am serious, because the current behaviour is totally
counterintuitive.  I really think that people will get bitten by this.
Actually, they probably have been, but are probably too embarrassed to
have admitted it!

peace & happiness,
martin