* It is now possible to execute a builder using a shell inside the Nix

store, rather than outside (such as /bin/sh).

  For instance, the Nix expression for the ATerm library now looks
  like this:

    {stdenv, fetchurl}:

    stdenv.mkDerivation {
      name = "aterm-2.0.5";
      builder = ./builder.sh;
      ...
    }

  where `mkDerivation' is a helper function in `stdenv' that massages
  the given attribute set into using the bash shell that is part of
  the standard environment:

    mkDerivation = attrs: derivation (att s // {
      builder = pkgs.bash ~ /bin/sh;
      args = ["-e" attrs.builder];
      stdenv = (...);
      system = (...).system;
    });

  Note that this makes it unnecessary to set the `stdenv' and `system'
  attributes, since `mkDerivation' already does that.


svn path=/nixpkgs/trunk/; revision=866

pkgs/development/libraries/aterm/builder.sh

@@ -1,6 +1,3 @@
-#! /bin/sh
-
 . $stdenv/setup
-
 configureFlags="--with-gcc"
 genericBuild

pkgs/development/libraries/aterm/default.nix

@@ -1,12 +1,10 @@
 {stdenv, fetchurl}:
 
-derivation {
+stdenv.mkDerivation {
   name = "aterm-2.0.5";
-  system = stdenv.system;
   builder = ./builder.sh;
   src = fetchurl {
     url = http://www.cwi.nl/projects/MetaEnv/aterm/aterm-2.0.5.tar.gz;
     md5 = "68aefb0c10b2ab876b8d3c0b2d0cdb1b";
   };
-  inherit stdenv;
 }

pkgs/stdenv/nix-linux/default.nix

@@ -1,19 +1,36 @@
 {stdenv, glibc, pkgs, genericStdenv, gccWrapper}:
 
-genericStdenv {
-  name = "stdenv-nix-linux";
-  preHook = ./prehook.sh;
-  initialPath = (import ../nix/path.nix) {pkgs = pkgs;};
+let {
 
-  inherit stdenv;
+  body =
 
-  gcc = gccWrapper {
-    name = pkgs.gcc.name;
-    nativeTools = false;
-    nativeGlibc = false;
-    inherit (pkgs) gcc binutils;
-    inherit stdenv glibc;
-  };
+    genericStdenv {
+      name = "stdenv-nix-linux";
+      preHook = ./prehook.sh;
+      initialPath = (import ../nix/path.nix) {pkgs = pkgs;};
+
+      inherit stdenv;
+
+      gcc = gccWrapper {
+        name = pkgs.gcc.name;
+        nativeTools = false;
+        nativeGlibc = false;
+        inherit (pkgs) gcc binutils;
+        inherit stdenv glibc;
+      };
+
+      param1 = pkgs.bash;
+    }
+
+    # Add a utility function to produce derivations that use this
+    # stdenv and its the bash shell.
+    // {
+      mkDerivation = attrs: derivation (attrs // {
+        builder = pkgs.bash ~ /bin/sh;
+        args = ["-e" attrs.builder];
+        stdenv = body;
+        system = body.system;
+      });
+    };
 
-  param1 = pkgs.bash;
 }