* Through the magic of functional programming, let stdenv export a

function to regenerate itself with a different setup script.  This
  is useful for experimenting with changes to the setup script in
  specific packages without triggering a rebuild of everything.

* stdenv/generic/setup-latest.sh is a branch of setup.sh containing
  pending changes that will be merged into setup.sh eventually.

* setup-latest.sh: don't use tar's "z" and "j" flags.  Rather, call
  gzip and bunzip2 directly.

svn path=/nixpkgs/trunk/; revision=6066

pkgs/top-level/all-packages.nix

@@ -54,6 +54,16 @@ rec {
       );
     };
 
+  # Override the setup script of stdenv.  Useful for testing new
+  # versions of the setup script without causing a rebuild of
+  # everything.
+  #
+  # Example:
+  #   randomPkg = (import ../bla) { ...
+  #     stdenv = overrideSetup stdenv ../stdenv/generic/setup-latest.sh;
+  #   };
+  overrideSetup = stdenv: setup: stdenv.regenerate setup;
+
 
   ### STANDARD ENVIRONMENT