Development shells with Nix: four quick examples

I wanted to use GoCV for one of my projects (to find and&#xA;extract paper documents from within a larger scan), without permanently having&#xA;OpenCV on my system. &#xA; This seemed like a good example use-case to demonstrate a couple of Nix commands&#xA;I like to use, covering quick interactive one-off dev shells to fully&#xA;declarative, hermetic, reproducible, shareable dev shells. &#xA;…