Relative Line Numbers In Emacs

Question

Does anyone know how if something like this Vim Relative Line Numbers exists for emacs? I use vimpulse, and man, that would be super handy to have! I know some lisp, so if it doesn't, I could try to make my own, if I got a point in the right direction.

Update: Thanks to the correct response, I came up with this, that will show 1 for the current line, and -1 for the previous line, for combining with vimpulse yanks and deletes.

Thanks a ton to all who helped! I know it is not exactly what Vim does, but what good is the Relative line numbers in vim that start at zero?? Silly vim.

(defvar my-linum-current-line-number 0)

(setq linum-format 'my-linum-relative-line-numbers)

(defun my-linum-relative-line-numbers (line-number)
  (let ((test2 (1+ (- line-number my-linum-current-line-number))))
    (propertize
     (number-to-string (cond ((<= test2 0) (1- test2))
                             ((> test2 0) test2)))
     'face 'linum)))

(defadvice linum-update (around my-linum-update)
  (let ((my-linum-current-line-number (line-number-at-pos)))
    ad-do-it))
(ad-activate 'linum-update)

Answer 1

In Emacs 26.1, there's a built-in line number mode (display-line-numbers-mode). Enable it and set (setq display-line-numbers 'relative) to use relative line numbers.