anchor.diff:  
         # A Nixpkgs overlay that overrides the 'nix' and
         # 'nix.perl-bindings' packages.
  -      overlay = overlayFor (p: p.stdenv);
  +      overlays.default = overlayFor (p: p.stdenv);
   
         hydraJobs = {
   
  
positive.code:           )
        );
  
        forAllStdenvs = stdenvs: f: nixpkgs.lib.genAttrs stdenvs (stdenv: f stdenv);
  
        # Memoize nixpkgs for different platforms for efficiency.
        nixpkgsFor =
  
negative.code:           nixpkgsFor.${system}."${stdenvName}Packages".nix
        ) stdenvs)));
  
        devShells = forAllSystems (system:
          forAllStdenvs (stdenv:
            with nixpkgsFor.${system};
            with commonDeps pkgs;
            nixpkgsFor.${system}.${stdenv}.mkDerivation {
              name = "nix";
  
              outputs = [ "out" "dev" "doc" ];
  
              nativeBuildInputs = nativeBuildDeps;
              buildInputs = buildDeps ++ propagatedDeps ++ awsDeps;
  
              inherit configureFlags;
  
              enableParallelBuilding = true;
  
              installFlags = "sysconfdir=$(out)/etc";
  
              shellHook =
                ''
                  PATH=$prefix/bin:$PATH
                  unset PYTHONPATH
                  export MANPATH=$out/share/man:$MANPATH
  
                  # Make bash completion work.
                  XDG_DATA_DIRS+=:$out/share
                '';
            }
          )
          // { default = self.devShells.${system}.stdenv; }
        );
  
    };
  }
  