anchor.diff:    postInstall = ''
       substituteInPlace $out/share/applications/quaternion.desktop \
         --replace 'Exec=quaternion' "Exec=$out/bin/quaternion"
  -
  -    rm $out/share/icons/hicolor/icon-theme.cache
     '';
   
     meta = with lib; {
  -    homepage = https://matrix.org/docs/projects/client/quaternion.html;
       description = "Cross-platform desktop IM client for the Matrix protocol";
  -    license = licenses.gpl3;
  +    homepage    = https://matrix.org/docs/projects/client/quaternion.html;
  +    license     = licenses.gpl3;
       maintainers = with maintainers; [ peterhoeg ];
       inherit (qtbase.meta) platforms;
       inherit version;
  
positive.code:   # derivation.
  
    src = fetchgit {
      url             = "https://github.com/Fxrh/Quaternion.git";
      rev             = "c35475a6755cdb75e2a6c8ca5b943685d07d9707";
      sha256          = "0cm5j4vdnp5cljfnv5jqf89ccymspaqc6j9bb4c1x891vr42np0m";
      fetchSubmodules = true;
    };
  
  
negative.code: 
  mkDerivation rec {
    name = "quaternion-git-${version}";
    version = "2017-06-29";
  
    # quaternion and tensor share the same libqmatrixclient library as a git submodule
    #
  