# rebase is a helper which takes all files/dirs under oldroot, and
# creates a new derivation with those files/dirs copied under newroot
# (where newroot is a relative path to the root of the derivation).

{

  stdenv,

}: name: oldroot: newroot: stdenv.mkDerivation {

  inherit name oldroot newroot;

  builder = builtins.toFile "builder.sh" ''
    source $stdenv/setup
    mkdir -p "$out"/"$newroot"
    cp -rL "$oldroot"/* "$out"/"$newroot"
  '';
}