diff & patch

[oleks]

As you mark student work, you might come to realise that your initial remarks template is missing, or has a wrong, or ill-phrased judgement. A diff and patch pair of commands would allow to compute the difference between two remarks files (e.g., a filled in remarks file and a template), and patch in changes, as needed.

This related to #13, but closing that issue now due to its age.