src/cli/context.js/Context/performanceTestFlag
class Context:  get performanceTestFlag() {
    const { debugBenchmark, debugRepeat } = this.argv;
    /* istanbul ignore next */
    if (debugBenchmark) {
      return {
        name: "--debug-benchmark",
        debugBenchmark: true,
      };
    }

    if (debugRepeat > 0) {
      return {
        name: "--debug-repeat",
        debugRepeat,
      };
    }

    const { PRETTIER_PERF_REPEAT } = process.env;
    if (PRETTIER_PERF_REPEAT && /^\d+$/.test(PRETTIER_PERF_REPEAT)) {
      return {
        name: "PRETTIER_PERF_REPEAT (environment variable)",
        debugRepeat: Number(PRETTIER_PERF_REPEAT),
      };
    }
  }