code: func registerFlags(c *cli.Config, f *flag.FlagSet) {
  	f.StringVar(&c.CertFile, "cert", "", "Client certificate that contains the public key")
  	f.StringVar(&c.Domain, "domain", "", "remote server domain name")
  	f.StringVar(&c.Serial, "serial", "", "certificate serial number")
  	f.StringVar(&c.AKI, "aki", "", "certificate issuer (authority) key identifier")
  	f.StringVar(&c.DBConfigFile, "db-config", "", "certificate db configuration file")
  }
docs: // registerFlags defines all cfssl command flags and associates their values with variables.