core/pkgs/build-support/fetchdarcs/default.nix

{
  stdenvNoCC,
  darcs,
  cacert,
  lib,
}:

lib.makeOverridable (
  {
    url,
    rev ? null,
    context ? null,
    sha256 ? "",
    name ? "fetchdarcs",
  }:

  stdenvNoCC.mkDerivation {
    builder = ./builder.sh;
    nativeBuildInputs = [
      cacert
      darcs
    ];

    outputHashAlgo = "sha256";
    outputHashMode = "recursive";
    outputHash = sha256;

    inherit
      url
      rev
      context
      name
      ;
  }
)