The `ServeCommand` will let you serve your site locally for development. You
can specify `--port`, `--host` and `--baseurl` options if you wish to change the
defaults.
Additionally the `BuildCommand` will be called before the processing of the
serve command, this makes sure that the site is actually built. This means you
are able to pass the `--watch` option to auto-regenerate your site, even while
serving it locally.
The `BuildCommand` class is responsible for handling the building of the site.
It can also optionally watch for changes to files and regenerate the site if
needed.
The `Command` class holds any methods which are used by any command
implementation.