(defun jay/count-heading-lines ()
    "Count lines in this heading and append to line as a tag"
    (interactive)
    (let (here there)
      (save-excursion
        (setq here (line-number-at-pos (point)))
        (save-excursion
          (org-forward-heading-same-level 1)
          (setq there (line-number-at-pos (point)))))
      (org-set-tags-to (number-to-string (- there here 1)))))