src/vs/workbench/contrib/search/common/searchModel.ts/FolderMatch/onFolderChange
class FolderMatch:	public onFolderChange(folderMatch: FolderMatchWithResource, event: IChangeEvent): void {
		if (!this._folderMatches.has(folderMatch.resource)) {
			this.doAddFolder(folderMatch);
		}
		if (folderMatch.isEmpty()) {
			this._folderMatches.delete(folderMatch.resource);
			folderMatch.dispose();
		}

		this._onChange.fire(event);
	}