Unable to use with nix that doesn't support flakes

[takeda]

NixOS 21.11 still uses Nix 2.3 by default.

When trying to reference the repo I'm getting following error:

fetching Git repository '/nix/store/p04jlkgwqm5kiwphm12zbvb485xzpcd8-source'fatal: '/nix/store/p04jlkgwqm5kiwphm12zbvb485xzpcd8-source' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

I believe this has to do with the code in default.nix:

(import (fetchTarball https://github.com/edolstra/flake-compat/archive/master.tar.gz) {
  src = builtins.fetchGit ./.;
}).defaultNix

Instead of src = builtins.fetchGit ./.; it should be src = ./.;

Or even better use the new recommendations from https://github.com/edolstra/flake-compat