Method run

tools/make_single_header.cpp:34–38

struct include_processor {

  static auto run(fs::path const &start_file) -> std::string {
    auto start_path = start_file;
    start_path.remove_filename();
    return include_processor{std::move(start_path)}.process_one(start_file);
  }

 private:
  struct replacement {