* maintainers/scripts/gnu/gnupdate.scm (attribute-value,
derivation-source, derivation-output-path, source-output-path,
derivation-source-output-path, find-attribute-by-name,
find-package-by-attribute-name, stdenv-package, package-requisites):
New procedures.
(%options): Add `--select'.
(main): Compute the source output paths of `stdenv'. Filter out
packages that are/aren't in `stdenv', depending on the `--select'
option.
svn path=/nixpkgs/trunk/; revision=22453
073c01503a