Echo Area

The primary way of identifying which part of an org-mode document a change occurs in seems to me to be the heading. So, in your $HOME/.gitconfig put:

[diff "org"]
      xfuncname = "^\\*+.*"

Which should show any lines starting with one or more * characters. And then in $XDG_CONFIG_HOME/git/attributes or $HOME/.config/git/attributes put:

*.org   diff=org

For anything that resembles lisp (so Common Lisp, Emacs Lisp, Hy, scheme, etc.) I would think that the easiest thing to do is just see the closes top-level form. So, in your $HOME/.gitconfig put:

[diff "lisp"]
      xfuncname = "^\\([^ ]+ [^ ]+"

Which should show the opening parenthesis and the first two words. For example:

(defun some-function-name
(defclass my-awesome-class
(define-route this-strange-route

And then put in your $XDG_CONFIG_HOME/git/attributes or $HOME/.config/git/attributes:

*.lisp  diff=lisp
*.el    diff=lisp
*.hy    diff=lisp
*.scm   diff=lisp

And possibly any other lisp-like language files you can think of.