self: super:
let
  fallback-git-cache = self.python3Packages.callPackage
    ({ buildPythonPackage, fetchgit, git, backoff, mypy, }:
      buildPythonPackage rec {
        pname = "git-cache";
        version = "1.5.0";
        src = fetchgit {
          url = "https://git.scottworley.com/pub/git/git-cache";
          rev = "v${version}";
          hash = "sha256-g4TS/zX3e29Q3ThsCAX2wLLlYbi8fdux5uqAc+b/Oww=";
        };
        propagatedBuildInputs = [ backoff ];
        nativeCheckInputs = [ git mypy ];
        doCheck = true;
        checkPhase = "./test.sh";
      }) { };

  fallback-pinch = self.python3Packages.callPackage
    ({ buildPythonPackage, fetchgit, nix, git, mypy, git-cache, }:
      buildPythonPackage rec {
        pname = "pinch";
        version = "3.3.1";
        src = fetchgit {
          url = "https://git.scottworley.com/pub/git/pinch";
          rev = "v${version}";
          hash = "sha256-fVlHwQX2o8GYZ/Oq5/m5v2L+KNpFoKWD8MbH4A3cV0s=";
        };
        propagatedBuildInputs = [ git-cache ];
        nativeCheckInputs = [ nix git mypy ];
        doCheck = true;
        checkPhase = "./test.sh";
      }) { git-cache = self.python3Packages.git-cache or fallback-git-cache; };

in { pinch = super.pinch or fallback-pinch; }