{stdenv, fetchgit, mercurial, coreutils, git, makeWrapper, subversion}:

stdenv.mkDerivation {
  name = "fast-export";

  src = fetchgit {
    url = "git://repo.or.cz/fast-export.git";
    rev = "refs/heads/master";
  };

  buildInputs = [mercurial.python mercurial makeWrapper subversion];

  buildPhase="true"; # skip svn for now

  # TODO also support svn stuff
  # moving .py files into lib directory so that you can't pick the wrong file from PATH.
  # This requires redefining ROOT
  installPhase = ''
    sed -i "s@/usr/bin/env.*@$(type -p python)@" *.py
    l=$out/libexec/git-fast-export
    mkdir -p $out/{bin,doc/git-fast-export} $l
    mv *.txt $out/doc/git-fast-export
    sed -i "s@ROOT=.*@ROOT=$l@" *.sh
    mv *.sh $out/bin
    mv *.py $l
    for p in $out/bin/*.sh; do
      wrapProgram $p \
        --prefix PYTHONPATH : "$(echo ${mercurial}/lib/python*/site-packages):$(echo ${mercurial.python}/lib/python*/site-packages)${stdenv.lib.concatMapStrings (x: ":$(echo ${x}/lib/python*/site-packages)") mercurial.pythonPackages}" \
        --prefix PATH : "$(dirname $(type -p python))":$l
    done
  '';

  # usage: 
  meta = {
      description = "import svn, mercurial into git";
      homepage = "http://repo.or.cz/w/fast-export.git";
      license = "?"; # the .py file is GPLv2
  };
}