iso-image: Combine GNOME and Plasma flavors

This allows users to choose between the two during bootup rather than
at download time.

nixos/modules/installer/cd-dvd/installation-cd-graphical-calamares-gnome.nix

···
 # This module defines a NixOS installation CD that contains GNOME.
 
-{ pkgs, ... }:
+{ lib, pkgs, ... }:
 
 {
   imports = [ ./installation-cd-graphical-calamares.nix ];
 
-  isoImage.edition = "gnome";
+  isoImage.edition = lib.mkDefault "gnome";
 
   services.xserver.desktopManager.gnome = {
     # Add Firefox and other tools useful for installation to the launcher

nixos/modules/installer/cd-dvd/installation-cd-graphical-calamares-plasma5.nix

···
 # This module defines a NixOS installation CD that contains X11 and
 # Plasma 5.
 
-{ pkgs, ... }:
+{ lib, pkgs, ... }:
 
 {
   imports = [ ./installation-cd-graphical-calamares.nix ];
 
-  isoImage.edition = "plasma5";
+  isoImage.edition = lib.mkDefault "plasma5";
 
   services.xserver.desktopManager.plasma5 = {
     enable = true;

nixos/modules/installer/cd-dvd/installation-cd-graphical-calamares-plasma6.nix

···
 # This module defines a NixOS installation CD that contains Plasma 6.
 
-{ pkgs, ... }:
+{ lib, pkgs, ... }:
 
 {
   imports = [ ./installation-cd-graphical-calamares.nix ];
 
-  isoImage.edition = "plasma6";
+  isoImage.edition = lib.mkDefault "plasma6";
 
   services.desktopManager.plasma6.enable = true;
 

nixos/modules/installer/cd-dvd/installation-cd-graphical-combined.nix

···
+# This configuration uses a specialisation for each desired boot
+# configuration, and a common parent configuration for all of them
+# that's hidden. This allows users to import this module alongside
+# their own and get the full array of specialisations inheriting the
+# users' settings.
+
+{ lib, ... }:
+{
+  imports = [ ./installation-cd-base.nix ];
+  isoImage.edition = "graphical";
+  isoImage.showConfiguration = lib.mkDefault false;
+
+  specialisation = {
+    gnome.configuration =
+      { config, ... }:
+      {
+        imports = [ ./installation-cd-graphical-calamares-gnome.nix ];
+        isoImage.showConfiguration = true;
+        isoImage.configurationName = "GNOME (Linux LTS)";
+      };
+
+    gnome_latest_kernel.configuration =
+      { config, ... }:
+      {
+        imports = [
+          ./installation-cd-graphical-calamares-gnome.nix
+          ./latest-kernel.nix
+        ];
+        isoImage.showConfiguration = true;
+        isoImage.configurationName = "GNOME (Linux ${config.boot.kernelPackages.kernel.version})";
+      };
+
+    plasma.configuration =
+      { config, ... }:
+      {
+        imports = [ ./installation-cd-graphical-calamares-plasma6.nix ];
+        isoImage.showConfiguration = true;
+        isoImage.configurationName = "Plasma (Linux LTS)";
+      };
+
+    plasma_latest_kernel.configuration =
+      { config, ... }:
+      {
+        imports = [
+          ./installation-cd-graphical-calamares-plasma6.nix
+          ./latest-kernel.nix
+        ];
+        isoImage.showConfiguration = true;
+        isoImage.configurationName = "Plasma (Linux ${config.boot.kernelPackages.kernel.version})";
+      };
+  };
+}

nixos/modules/installer/cd-dvd/installation-cd-graphical-gnome.nix

···
 # This module defines a NixOS installation CD that contains GNOME.
 
-{ ... }:
+{ lib, ... }:
 
 {
   imports = [ ./installation-cd-graphical-base.nix ];
 
-  isoImage.edition = "gnome";
+  isoImage.edition = lib.mkDefault "gnome";
 
   services.xserver.desktopManager.gnome = {
     # Add Firefox and other tools useful for installation to the launcher

nixos/modules/installer/cd-dvd/installation-cd-graphical-plasma5.nix

···
 # This module defines a NixOS installation CD that contains X11 and
 # Plasma 5.
 
-{ pkgs, ... }:
+{ lib, pkgs, ... }:
 
 {
   imports = [ ./installation-cd-graphical-base.nix ];
 
-  isoImage.edition = "plasma5";
+  isoImage.edition = lib.mkDefault "plasma5";
 
   services.xserver.desktopManager.plasma5 = {
     enable = true;

nixos/release.nix

···
     inherit system;
   });
 
-  iso_plasma5 = forMatchingSystems supportedSystems (system: makeIso {
-    module = ./modules/installer/cd-dvd/installation-cd-graphical-calamares-plasma5.nix;
-    type = "plasma5";
-    inherit system;
-  });
-
-  iso_plasma6 = forMatchingSystems supportedSystems (system: makeIso {
-    module = ./modules/installer/cd-dvd/installation-cd-graphical-calamares-plasma6.nix;
-    type = "plasma6";
-    inherit system;
-  });
-
-  iso_gnome = forMatchingSystems supportedSystems (system: makeIso {
-    module = ./modules/installer/cd-dvd/installation-cd-graphical-calamares-gnome.nix;
-    type = "gnome";
+  iso_graphical = forAllSystems (system: makeIso {
+    module = ./modules/installer/cd-dvd/installation-cd-graphical-combined.nix;
+    type = "graphical";
     inherit system;
   });