{
  unstable_pkgs,
  stable_pkgs,
  extra_lib,
}: let
  inherit (unstable_pkgs) lib;

  mergePkgs = pkgs: lib.callPackageWith (extra_lib.warnMerge pkgs in_tree_pkgs "the ./pkgs/by-name set");
  callPackageStable = lib.callPackageWith (mergePkgs stable_pkgs);
  callPackageUnstable = lib.callPackageWith (mergePkgs unstable_pkgs);

  in_tree_pkgs = extra_lib.mkByName {
    baseDirectory = ./by-name;
    fileName = "package.nix";
    finalizeFunction = name: value:
      if value.stable
      then callPackageStable value.pkg {}
      else callPackageUnstable value.pkg {};
  };
in
  in_tree_pkgs