Drupal 8 tip of the day: replace hook_drush_command() by a YAML file

One of the big trends during the Drupal 8 creation has been the replacement of info hooks by two main mechanisms: annotations, and YAML files. In that light, hook_drush_command(), as the CLI equivalent of the late hook_menu, replaced by various YAML files, looks just like a perfect candidate for replacement by a commands section in some mymodule.drush.yml configuration file. Turns out it is incredibly easy to achieve. Let's see how to kill some hundred lines of code real fast !