function sort( a, b ) {
	if ( a.file < b.file ) {
		return 1;
	}
	if ( a.file > b.file ) {
		return -1;
	}
	return 0;
}
Sort function for ensuring deterministic comparison order.

@private
@param {Object} a - first value
@param {Object} b - second value
@returns {number} value indicating whether to sort `a` before `b`