anchor.diff:  
     /* Map an attribute of the form `foo = [platforms...]'  to `testOn
        [platforms...] (pkgs: pkgs.foo)'. */
  -  mapTestOn = pkgs.lib.mapAttrsRecursive
  -    (path: value: testOn value (pkgs: pkgs.lib.getAttrFromPath path pkgs));
  +  mapTestOn = pkgs.lib.mapAttrsRecursiveCond
  +    (as: !(as ? type && as.type == "job"))
  +    (path: value:
  +      let
  +        job = toJob value;
  +        getPkg = pkgs:
  +          pkgs.lib.addMetaAttrs { schedulingPriority = toString job.schedulingPriority; }
  +          (pkgs.lib.getAttrFromPath path pkgs);
  +      in testOn job.systems getPkg);
   
     /* Common platform groups on which to test packages. */
     linux = ["i686-linux" "x86_64-linux"];
  
positive.code:   allPackages = import ./all-packages.nix;
  
    pkgs = allPackages {};
  
    /* Perform a job on the given set of platforms.  The function `f' is
       called by Hydra for each platform, and should return some job
  
negative.code:   file = all;
    findutils = all;
    firefox2 = linux;
    firefox3 = prio 150 linux;
    flex = all;
    flex2535 = all;
    gawk = all;
  