Re: undo gone in dired buffers

[Richard Stallman]

    C-x d /tmp RET
    M-! touch 00a RET
    g --> Now yu should see a file named 00a
    C-x C-q
    undo --> Now you don't see the file 00a any more

The operation undone was the deletion of the old buffer contents and
insertion of the new contents.  No wonder I turned off undo for that.
The comparable operation for files discards undo data also.