anchor.diff:  
     PKG_CONFIG_UDEV_UDEVDIR = "lib/udev";
     mesonFlags = lib.optionals (!fuseSupport) [ "-Dfuse=false" ]
  -               ++ lib.optionals (!udevSupport) [ "-Dudev=false" ]
  -               ++ lib.optionals (!selinuxSupport) [ "-Dselinux=false" ];
  +    ++ lib.optionals (!udevSupport) [ "-Dudev=false" ]
  +    ++ lib.optionals (!selinuxSupport) [ "-Dselinux=false" ];
   
     doCheck = true;
     preCheck = ''
  
positive.code: { lib, stdenv, fetchFromGitHub
  , meson, ninja, pkg-config, python3, sphinx
  , acl, curl, fuse, libselinux, udev, xz, zstd
  , fuseSupport ? true
  , selinuxSupport ? true
  , udevSupport ? true
  , glibcLocales, rsync
  }:
  
  stdenv.mkDerivation {
  
negative.code: 
    meta = with lib; {
      description = "Content-Addressable Data Synchronizer";
      homepage = "https://github.com/systemd/casync";
      license = licenses.lgpl21;
      platforms = platforms.linux;
      maintainers = with maintainers; [ flokli ];
    };
  }
  