From 06bfb319fe0d16474483ed5d9343740c93429842 Mon Sep 17 00:00:00 2001
From: Nicolas Pierron <nicolas.b.pierron@gmail.com>
Date: Sat, 8 May 2010 17:18:26 +0000
Subject: [PATCH] Add extra module argument to provide a nesting.clone option. 
 This option does the same as nesting.children except that each configuration
 inherits from the top-level configuration.

svn path=/nixos/trunk/; revision=21663
---
 lib/eval-config.nix                     |  2 +-
 modules/system/activation/no-clone.nix  | 13 +++++++++++
 modules/system/activation/top-level.nix | 30 ++++++++++++++++---------
 3 files changed, 34 insertions(+), 11 deletions(-)
 create mode 100644 modules/system/activation/no-clone.nix

diff --git a/lib/eval-config.nix b/lib/eval-config.nix
index 77c20caf604..49057f2d6da 100644
--- a/lib/eval-config.nix
+++ b/lib/eval-config.nix
@@ -30,7 +30,7 @@ rec {
   # These are the extra arguments passed to every module.  In
   # particular, Nixpkgs is passed through the "pkgs" argument.
   extraArgs = extraArgs_ // {
-    inherit pkgs;
+    inherit pkgs modules baseModules;
     modulesPath = ../modules;
     servicesPath = services;
   };
diff --git a/modules/system/activation/no-clone.nix b/modules/system/activation/no-clone.nix
new file mode 100644
index 00000000000..ca106807513
--- /dev/null
+++ b/modules/system/activation/no-clone.nix
@@ -0,0 +1,13 @@
+# This configuration is not made to figure inside the module-list.nix to
+# allow clone of the first level.
+{pkgs, ...}:
+
+with pkgs.lib;
+
+{
+  boot.loader.grub.device = mkOverride 0 {} "";
+  # undefined the obsolete name of the previous option.
+  boot.grubDevice = mkOverride 0 {} pkgs.lib.mkNotdef;
+  nesting.children = mkOverride 0 {} [];
+  nesting.clone = mkOverride 0 {} [];
+}
diff --git a/modules/system/activation/top-level.nix b/modules/system/activation/top-level.nix
index 871172f3039..262a3bb9ae7 100644
--- a/modules/system/activation/top-level.nix
+++ b/modules/system/activation/top-level.nix
@@ -1,4 +1,4 @@
-{pkgs, config, ...}:
+{pkgs, config, modules, baseModules, ...}:
 
 let
 
@@ -18,6 +18,14 @@ let
       '';
     };
 
+    nesting.clone = pkgs.lib.mkOption {
+      default = [];
+      description = ''
+        Additional configurations to build based on the current
+        configuration which is has a lower priority.
+      '';
+    };
+
     system.boot.loader.id = pkgs.lib.mkOption {
       default = "";
       description = ''
@@ -71,18 +79,20 @@ let
   # you can provide an easy way to boot the same configuration 
   # as you use, but with another kernel
   # !!! fix this
-  children = with pkgs.lib;
+  cloner = inheritParent: list: with pkgs.lib;
     map (childConfig:
       (import ../../../lib/eval-config.nix {
-        modules = [
-          (recursiveUpdate childConfig {
-            boot.loader.grub.device = "";
-            # undefined the obsolete name of the previous option.
-            boot.grubDevice = pkgs.lib.mkNotdef;
-          })
-        ] ++ attrByPath ["require"] [] childConfig;
+        inherit baseModules;
+        modules =
+           (optionals inheritParent modules)
+        ++ [ ./no-clone.nix ]
+        ++ [ childConfig ];
       }).config.system.build.toplevel
-    ) config.nesting.children;
+    ) list;
+
+  children =
+     cloner false config.nesting.children
+  ++ cloner true config.nesting.clone;
 
 
   systemBuilder =