still trying to understand undocumented 'previous hydra build' option

sinara-systems.nix

@@ -1,6 +1,29 @@
 { pkgs ? import <nixpkgs> {}}:
-{ mainBuild }:
 
+let
+  mainChannel = import <mainChannel>;
+  #artiq-board = import <mainChannel/artiq-board.nix> { inherit pkgs; };
+  #conda-artiq-board = import <mainChannel/conda-artiq-board.nix> { inherit pkgs; };
+
+  #target = "kasli";
+
+  #variants = ["berkeley" "mitll2" "mitll" "nudt" "sysu" "tsinghua2" "tsinghua" "unsw" "ustc" "wipm"];
+  #jobs = pkgs.lib.lists.foldr (variant: start:
+  #  let
+  #    json = ../. + "/${variant}.json";
+  #    boardBinaries = conda-artiq-board {
+  #      inherit target variant;
+  #      buildCommand = "python -m artiq.gateware.targets.kasli_generic ${json}";
+  #    };
+  #  in
+  #    start // {
+  #      "artiq-board-${target}-${variant}" = boardBinaries;
+  #      "conda-artiq-board-${target}-${variant}" = conda-artiq-board {
+  #        boardBinaries = boardBinaries;
+  #        inherit target variant;
+  #    };
+  #}) {} variants;
+in
   {
-  fooxx = pkgs.runCommand "xxxxabcd" { } "echo ${mainBuild} > $out";
+    foo = pkgs.runCommand "xxxxabcd" { } "echo ${mainChannel} > $out";
   }