src/vs/workbench/contrib/search/common/queryBuilder.ts/QueryBuilder/file
class QueryBuilder:	file(folders: (IWorkspaceFolderData | URI)[], options: IFileQueryBuilderOptions = {}): IFileQuery {
		const commonQuery = this.commonQuery(folders, options);
		return <IFileQuery>{
			...commonQuery,
			type: QueryType.File,
			filePattern: options.filePattern
				? options.filePattern.trim()
				: options.filePattern,
			exists: options.exists,
			sortByScore: options.sortByScore,
			cacheKey: options.cacheKey,
		};
	}