Question

Does anyone have an emacs lisp hack that would allow the creation of a new directory on the fly during dired-do-copy or dired-do-rename? I understand that it can be created prior to running one of these two commands. Extra points for some type of “Are you sure…” prompt.

Answer 1

It look like a case of applying an advice. The question being: what to
advice. Looking at the dired code, it seem that the correct target is
dired-mark-read-file-name that is used to read the destination
file-name. This will work:

(defadvice dired-mark-read-file-name (after rv:dired-create-dir-when-needed (prompt dir op-symbol arg files &optional default) activate)
  (when (member op-symbol '(copy move))
    (let ((directory-name (if (< 1 (length files))
                              ad-return-value
                              (file-name-directory ad-return-value))))
      (when (and (not (file-directory-p directory-name))
                 (y-or-n-p (format "directory %s doesn't exist, create it?" directory-name)))
        (make-directory directory-name t)))))

Note that maybe the first when (when (member op-symbol '(copy move))) could be removed for this to apply to more case of file creation in dired. But I’m not sure of when dired-mark-read-file-name is called, So I let this test there to reduce potential unwanted side-effect