In preparation for Agaric's latest migration training, we've seen again that getting a development environment suitable for working on Drupal with Composer is a big road block. For that reason, here are instructions for getting it all going, suitable for our training or for working on Drupal in a code sprint, with only one hard requirement: PHP.
The command line provides so much power. We cover none of that power here, instead showing how to open the door—to open your terminal—on several operating systems.