Merge "Add --apply-only to benchmarks" into main

        # Preroll builds

        for i in range(benchmark.preroll):

            if not self._options.ApplyOnly():

                ns = self._run_build(lunch, benchmark_log_dir.joinpath(f"pre_{i}"), benchmark)

                report.preroll_duration_ns.append(ns)

        sys.stderr.write(f"PERFORMING CHANGE: {benchmark.change.label}\n")

        if not self._options.DryRun():

            benchmark.change.change()

            if self._options.ApplyOnly():

                sys.stderr.write(f"NOT UNDOING CHANGE: {benchmark.change.label}\n")

                return

        try:

            # Measured build

                            help="Benchmarks to run.  Default suite will be run if omitted.")

        parser.add_argument("--list", action="store_true",

                            help="list the available benchmarks.  No benchmark is run.")

        parser.add_argument("--apply-only", action="store_true",

                            help="apply the change only, and then exit. Intended only for debugging.")

        parser.add_argument("--dist-one", action="store_true",

                            help="Copy logs and metrics to the given dist dir. Requires that only"

                                + " one benchmark be supplied. Postroll steps will be skipped.")

        if self._args.dist_one and len(self.Benchmarks()) != 1:

            self._error("--dist-one requires exactly one --benchmark.")

        # --apply-only forces --iterations=1

        if self.apply_only:

            self.iterations = 1

            if self.dist_one:

              self._error("--dist-one cannot be used with --apply-only.")

        if self._had_error:

            raise FatalError()

    def Tag(self):

        return self._args.tag

    def ApplyOnly(self):

        return self._args.apply_only

    def DryRun(self):

        return self._args.dry_run