src/vs/workbench/contrib/files/common/explorerFileNestingTrie.ts/PreTrie/add
class PreTrie:	add(key: string, value: string) {
		if (key === '') {
			this.value.add(key, value);
		} else if (key[0] === '*') {
			this.value.add(key, value);
		} else {
			const head = key[0];
			const rest = key.slice(1);
			let existing = this.map.get(head);
			if (!existing) {
				this.map.set(head, existing = new PreTrie());
			}
			existing.add(rest, value);
		}
	}