This is an extension of Symfony's Console application that simplifies the creation of simple, single-command PHP CLI scripts, saving a great deal of time and repeated code.
Just use Composer:
composer require aziraphale/symfony-single-command-application
And then it should autoload as everything else does, so the example class in /examples/TemplateCommand.php should work straight away.
See /examples/TemplateCommand.php to see how to use this class. It's probably easiest to simply copy TemplateCommand.php for every new single-command Symfony Console application that you create.