Function getenv_or_empty

populate-bucket/populate_bucket.cc:74–77

namespace {
std::string getenv_or_empty(char const* name) {
  auto value = std::getenv(name);
  return value == nullptr ? std::string{} : value;
}

std::tuple<po::variables_map, po::options_description> parse_command_line(
    int argc, char* argv[]) {