src/vs/workbench/api/common/extHostConfiguration.ts/lookUp
function lookUp(tree: any, key: string) {
	if (key) {
		const parts = key.split('.');
		let node = tree;
		for (let i = 0; node && i < parts.length; i++) {
			node = node[parts[i]];
		}
		return node;
	}
}