Allow filtering and sorting by tag in benchmark result formatting

        result += f"{m:2d}m "

    return result + f"{sec:2d}s"

def main(argv):

    parser = argparse.ArgumentParser(

            prog="format_benchmarks",

            allow_abbrev=False, # Don't let people write unsupportable scripts.

            description="Print analysis tables for benchmarks")

    parser.add_argument("--tags", nargs="*",

                        help="The tags to print, in order.")

    parser.add_argument("summaries", nargs="*",

                        help="A summary.json file or a directory in which to look for summaries.")

        s["datetime"] = dt

        s["date"] = datetime.date(dt.year, dt.month, dt.day)

    # Filter out tags we don't want

    if args.tags:

        summaries = [(f, s) for f, s in summaries if s.get("tag", "") in args.tags]

    # If they supplied tags, sort in that order, otherwise sort by tag

    if args.tags:

        tagsort = lambda tag: args.tags.index(tag)

    else:

        tagsort = lambda tag: tag

    # Sort the summaries

    summaries.sort(key=lambda s: (s[1]["date"], s[1]["branch"], s[1]["tag"]))

    summaries.sort(key=lambda s: (s[1]["date"], s[1]["branch"], tagsort(s[1]["tag"])))

    # group the benchmarks by column and iteration

    def bm_key(b):