function onCommand( error, results ) {
		if ( arguments.length === 0 ) {
			return repl._done();
		}
		if ( arguments.length === 1 ) {
			return repl._done( error );
		}
		repl._done( error, results );
	}
Callback invoked to confirm that a command has finished executing.

@private
@param {(Error|null)} [error] - execution error
@param {*} [results] - command results
@returns {void}