This script came about when I had a single Arch Linux machine with a large
amount of .pacnew files in /etc, to the point where some system services
weren't starting correctly.
I am more used to package managers which try to automatically merge /etc,
so I wrote this script trying to match the sort of 3-way merge prompt we get
with, say, sysmerge on OpenBSD. It does not rival that experience, but we can
at least invoke sdiff(1) to get most of the way there. YMMV. Provided
without warranty.