WIP: add postprocessing stages

garlic/postprocess/fetch.nix

@@ -0,0 +1,47 @@
+{
+  stdenv
+, rsync
+, openssh
+, nix
+, curl
+, garlicTools
+}:
+
+{
+  sshHost
+, prefix
+, experiment
+, garlicTemp
+}:
+
+with garlicTools;
+
+let
+  experimentStage = getExperimentStage experiment;
+  experimentName = baseNameOf (toString experimentStage);
+in
+  stdenv.mkDerivation {
+    name = "fetch";
+    preferLocalBuild = true;
+
+    buildInputs = [ rsync openssh curl ];
+    phases = [ "installPhase" ];
+
+    installPhase = ''
+      cat > $out << EOF
+      #!/bin/sh -e
+      mkdir -p ${garlicTemp}
+      export PATH=${rsync}/bin:${openssh}/bin:${nix}/bin
+      rsync -av \
+        --include='*/*/*.log' --include='*/*/*.json' --exclude='*/*/*' \
+        '${sshHost}:${prefix}/${experimentName}' ${garlicTemp}
+
+      res=\$(nix-build -E '(with import ./default.nix; garlic.getExpResult \
+        {experiment = "${experiment}"; garlicTemp = "${garlicTemp}"; })')
+
+      echo "The results for experiment ${experimentName} are at:"
+      echo "  \$res"
+      EOF
+      chmod +x $out
+    '';
+  }