[PROPOSAL] New function `org-headings-to-point' and displayer.

[Karl Fogel <kfogel@red-bean.com>]

Hi.  I've been using this for a while and find it very handy.

If people like this and want it in Org Mode, I'll do the rest of the work to package it up as a patch, with ChangeLog entry, NEWS, etc, and post it here for review before committing.

To try it out, just evaluate both functions and then run

  `M-x org-display-headings-to-point'

from somewhere deep in an org subtree.  Comments/feedback welcome.

Best regards,
-Karl

(defun org-headings-to-point ()
  "Return all the Org Mode headings leading to point."
  (when (not (eq major-mode 'org-mode))
    (error "ERROR: this only works in Org Mode"))
  (let ((headings (list (org-heading-components))))
    (save-excursion
      (save-match-data
        (save-restriction
          (widen)
          (while (org-up-heading-safe)
            (setq headings (cons (org-heading-components) headings)))))
      headings)))

(defun org-display-headings-to-point ()
  "Display Org Mode heading titles from level 1 to current subtree.
Display each title on its own line, indented proportionally to its level."
  (interactive)
  (let* ((heading-titles (mapcar (lambda (heading)
                                   (nth 4 heading))
                                 (org-headings-to-point)))
         (level 0)
         (hierarchy (mapcar (lambda (title)
                              (prog1
                                  (if (zerop level)
                                      (concat "• " title)
                                    (concat "\n" 
                                            (make-string (* level 2) ? )
                                            "→ " title))
                                (setq level (1+ level))))
                            heading-titles)))
    (display-message-or-buffer (string-join hierarchy))))