ds: link the resultTree in the dataset

garlic/pp/merge.nix

@@ -2,15 +2,22 @@
   stdenv
 }:
 
-experiments:
+datasets:
 
 with stdenv.lib;
 
 stdenv.mkDerivation {
-  name = "merge.json";
+  name = "merged-dataset";
   preferLocalBuild = true;
   phases = [ "installPhase" ];
+  inherit datasets;
   installPhase = ''
-    cat ${concatStringsSep " " experiments} >> $out
+    mkdir -p $out
+    n=1
+    for d in $datasets; do
+      ln -s $d $out/$n
+      let n=n+1
+      cat $d/dataset >> $out/dataset
+    done
   '';
 }