anchor.diff:      ++ optional (!cf.checkHostIP)            "  CheckHostIP no"
       ++ optional (cf.proxyCommand != null)    "  ProxyCommand ${cf.proxyCommand}"
       ++ optional (cf.proxyJump != null)       "  ProxyJump ${cf.proxyJump}"
  +    ++ map (file: "  IdentityFile ${file}") cf.identityFile
       ++ mapAttrsToList (n: v: "  ${n} ${v}") cf.extraOptions
     );
   
  
positive.code:       };
  
        identityFile = mkOption {
          type = types.nullOr types.str;
          default = null;
          description = ''
            Specifies a file from which the user identity is read.
          '';
        };
  
  
negative.code:     ++ optional cf.forwardX11Trusted         "  ForwardX11Trusted yes"
      ++ optional cf.identitiesOnly            "  IdentitiesOnly yes"
      ++ optional (cf.user != null)            "  User ${cf.user}"
      ++ optional (cf.certificateFile != null) "  CertificateFile ${cf.certificateFile}"
      ++ optional (cf.hostname != null)        "  HostName ${cf.hostname}"
      ++ optional (cf.addressFamily != null)   "  AddressFamily ${cf.addressFamily}"
  