Build a few NixOS system closures on Hydra

This will allow us to keep track of the evolution of closure sizes of
some typical configurations. (Hydra stores closure sizes in its
database.)

nixos/release.nix

@@ -78,6 +78,16 @@ let
         };
 
 
+  makeClosure = module: forAllSystems (system: (import ./lib/eval-config.nix {
+    inherit system;
+    modules = [ module ] ++ lib.singleton
+      ({ config, lib, ... }:
+      { fileSystems."/".device  = lib.mkDefault "/dev/sda1";
+        boot.loader.grub.device = lib.mkDefault "/dev/sda";
+      });
+  }).config.system.build.toplevel);
+
+
 in rec {
 
   channel =
@@ -242,4 +252,46 @@ in rec {
   tests.udisks2 = callTest tests/udisks2.nix {};
   tests.xfce = callTest tests/xfce.nix {};
 
+
+  /* Build a bunch of typical closures so that Hydra can keep track of
+     the evolution of closure sizes. */
+
+  closures = {
+
+    smallContainer = makeClosure ({ pkgs, ... }:
+      { boot.isContainer = true;
+        services.openssh.enable = true;
+      });
+
+    tinyContainer = makeClosure ({ pkgs, ... }:
+      { boot.isContainer = true;
+        imports = [ modules/profiles/minimal.nix ];
+      });
+
+    ec2 = makeClosure ({ pkgs, ... }:
+      { imports = [ modules/virtualisation/amazon-image.nix ];
+      });
+
+    kde = makeClosure ({ pkgs, ... }:
+      { services.xserver.enable = true;
+        services.xserver.displayManager.kdm.enable = true;
+        services.xserver.desktopManager.kde4.enable = true;
+      });
+
+    xfce = makeClosure ({ pkgs, ... }:
+      { services.xserver.enable = true;
+        services.xserver.desktopManager.xfce.enable = true;
+      });
+
+    # Linux/Apache/PostgreSQL/PHP stack.
+    lapp = makeClosure ({ pkgs, ... }:
+      { services.httpd.enable = true;
+        services.httpd.adminAddr = "foo@example.org";
+        services.postgresql.enable = true;
+        services.postgresql.package = pkgs.postgresql93;
+        environment.systemPackages = [ pkgs.php ];
+      });
+
+  };
+
 }