Diffing Parts Of Files

Every now and then I’ve felt the need to do a diff of parts of files,
rather than entire files. So I came up with the code in diffbuff.el in
this repo <https://gitlab.com/ldo/emacs-prefs>. Usage is simple:

* Select the first region to be diffed. Press super-D 1 to copy this
  to the diff buffer.
* Select the second region (in the same or a different buffer) to be
  diffed. Press super-D 2 to copy this to the diff buffer.
* Now press super-D d to do the diff, and be taken to the diff buffer
  to see the result, highlighted for convenience.