src/vs/workbench/contrib/tasks/common/taskConfiguration.ts/UUIDMap/getUUID
class UUIDMap:	public getUUID(identifier: string): string {
		let lastValue = this.last ? this.last[identifier] : undefined;
		let result: string | undefined = undefined;
		if (lastValue !== undefined) {
			if (Array.isArray(lastValue)) {
				result = lastValue.shift();
				if (lastValue.length === 0) {
					delete this.last![identifier];
				}
			} else {
				result = lastValue;
				delete this.last![identifier];
			}
		}
		if (result === undefined) {
			result = UUID.generateUuid();
		}
		let currentValue = this.current[identifier];
		if (currentValue === undefined) {
			this.current[identifier] = result;
		} else {
			if (Array.isArray(currentValue)) {
				currentValue.push(result);
			} else {
				let arrayValue: string[] = [currentValue];
				arrayValue.push(result);
				this.current[identifier] = arrayValue;
			}
		}
		return result;
	}