(defun github-current-line-numbers-range ()
  "Construct a github line number range from the current selection.
If no region is active, then just use the current line."
  (if (use-region-p)
      (concat "L" (number-to-string (line-number-at-pos (region-beginning))) "-L" (number-to-string (line-number-at-pos (region-end))))
    (concat "L" (number-to-string (line-number-at-pos (point))))))

(defun github-link-to-source ()
  "Links to the current source."
  (let ((path somehow-get-path-of-current-buffer)
        (orgin-url somehow-get-base-github-repo-url)
        (tree somehow-get-branch-of-current-checkout)
        (range (github-current-line-numbers-range)))
    (concat origin-url "/blob/" tree "/" path "#" range)))