src/vs/platform/files/common/fileService.ts/FileService/toWatchKey
class FileService:	private toWatchKey(provider: IFileSystemProvider, resource: URI, options: IWatchOptions): string {
		const { providerExtUri } = this.getExtUri(provider);

		return [
			providerExtUri.getComparisonKey(resource), 	// lowercase path if the provider is case insensitive
			String(options.recursive),					// use recursive: true | false as part of the key
			options.excludes.join()						// use excludes as part of the key
		].join();
	}