find-file-read-args: cursor's file as default in Dired

[Drew Adams]

Here's find-file-read-args:

(defun find-file-read-args (prompt mustmatch)
  (list (let ((find-file-default
               (and buffer-file-name
                    (abbreviate-file-name buffer-file-name))))
          (minibuffer-with-setup-hook
              (lambda () (setq minibuffer-default find-file-default))
            (read-file-name prompt nil default-directory mustmatch)))
        t))

Here's what it should be, so that `M-n' with `C-x C-f' gives you the file of
the cursor in Dired mode:

(defun find-file-read-args (prompt mustmatch)
  (list (let ((find-file-default
               (if (eq major-mode 'dired-mode)
                   (abbreviate-file-name (dired-get-file-for-visit))
                 (and buffer-file-name (abbreviate-file-name
buffer-file-name)))))
          (minibuffer-with-setup-hook
              (lambda () (setq minibuffer-default find-file-default))
            (read-file-name prompt nil default-directory mustmatch)))
        t))