private void print_help(const ref GetoptResult help_info)
{
    import core.runtime;
    import std.path : baseName;
    import std.algorithm : map, maxElement;

    writefln("Usage: %s [OPTION...]", Runtime.args[0].baseName);
    writeln();
    writeln("Convert D .lst coverage files to LCOV format.");
    writeln();
    writeln("Options:");

    string[] flags;
    foreach (opt; help_info.options)
        flags ~= opt.optShort ~ (opt.optShort.length ? ", " : "  ") ~ opt.optLong;

    size_t width = flags.map!(f => f.length).maxElement + 1;

    foreach (i, opt; help_info.options)
        writefln("  %-*s %s", width, flags[i], opt.help);
}