How to list all the commands in Drush 9 (aka: drush help)? I'm trying to list all the available commands by drush help, however I've the error:

$ drush help
  [Symfony\Component\Console\Exception\CommandNotFoundException]                                 
  Command  was not found. Pass --root or a @siteAlias in order to run Drupal-specific commands.


It was working in Drush 8, what's the equivalent command in Drush 9?
It is clearly a bug that drush help is printing a meaningless error message. Instead, it should tell you how to get the list of available commands.

drush list is the way to do that.