nixpkgs/pkgs/misc/bleeding-edge-fetch-info/mkcabal.nix

 args: with args; fetchurl { 
  url = http://mawercer.de/~nix/repos/mkcabal.tar.gz;
  sha256 = "9f231756c36b46d29516ed327a320837194799a76de4833dc6a5c88e5ccd1658";}