dired-mark-prompt
dired-mark-prompt is a compiled Lisp function in `dired.el
'.
(dired-mark-prompt ARG FILES)
Return a string suitable for use in a Dired prompt.
ARG is normally the prefix argument for the calling command.
FILES should be a list of file names.
The return value has a form like "foo.txt", "[next 3 files]",
or "* [3 files]".