Upgrading iRODS from 4.1.12 to 4.2.7

A short(!) choose-your-own adventure learning about the pitfalls of upgrading an iRODS system between two major versions.

You probably need to have installed iRODS and know what it is to get anything out of this!

This was inspired in large part by spending formative years playing Fighting Fantasy, and also by Robin Sloan's recent project;

With thanks to the iRODS Developers.