function command( pres ) {
	return onCommand;

	/**
	* Stops watching a source presentation file for changes.
	*
	* @private
	* @param {Error} [error] - error
	* @returns {void}
	*/
	function onCommand( error ) {
		if ( arguments.length ) {
			pres.unwatch( error );
			return;
		}
		pres.unwatch();
	}
}
Returns a callback to be invoked upon calling the `unwatch` command.

@private
@param {Presentation} pres - presentation instance
@returns {Function} callback