Fix trebuchet description

garlic/stages/experiment.nix

@@ -1,5 +1,6 @@
 {
   stdenv
+, garlicTools
 }:
 
 {
@@ -7,20 +8,11 @@
 }:
 
 with stdenv.lib;
+with garlicTools;
 
 let
-  stageProgram = stage:
-    if stage ? programPath
-    then "${stage}${stage.programPath}" else "${stage}";
-
   unitsString = builtins.concatStringsSep "\n"
     (map (x: "${stageProgram x}") units);
-
-  desc = builtins.concatStringsSep "\n"
-  (map (x: ''
-    #    ${x}
-    ${x.desc}'') units);
-
 in
 stdenv.mkDerivation {
   name = "experiment";
@@ -28,14 +20,11 @@ stdenv.mkDerivation {
   preferLocalBuild = true;
   dontPatchShebangs = true;
   inherit units;
-  inherit desc;
 
   installPhase = ''
     cat > $out << EOF
     #!/bin/sh
 
-    ${desc}
-
     # This is an experiment formed by the following units:
     ${unitsString}
     EOF

garlic/stages/isolate/default.nix

@@ -21,6 +21,7 @@ stdenv.mkDerivation {
   dontPatchShebangs = true;
   programPath = "/bin/stage1";
   inherit nixPrefix clusterName nixtools busybox;
+  inherit nextStage;
   program = stageProgram nextStage;
   desc = "#  $out\n" + (if builtins.hasAttr "desc" nextStage then nextStage.desc else "");
   out = "$out";

garlic/stages/trebuchet.nix

@@ -13,14 +13,17 @@
 , targetCluster ? "mn4"
 }:
 
+with garlicTools;
+
 let
-  program = garlicTools.stageProgram nextStage;
+  program = stageProgram nextStage;
 in
 stdenv.mkDerivation {
   name = "trebuchet";
   phases = [ "installPhase" ];
   preferLocalBuild = true;
   dontPatchShebangs = true;
+  inherit nextStage;
   installPhase = ''
     cat > $out <<EOF
     #!/bin/sh -e
@@ -29,8 +32,9 @@ stdenv.mkDerivation {
     # Take a look at ${program}
     # to see what is being executed.
 
-    #  $out
-    ${nextStage.desc}
+    # This trebuchet launches the following experiment in an isolated
+    # environment:
+    #  ${nextStage.nextStage}
 
     nixtools=${nixPrefix}${nixtools}/bin
     runexp=\$nixtools/${targetCluster}/runexp