{
  programs.git = {
    enable = true;
    userName = "John Doe";
    userEmail = "user@example.org";

    signing = {
      signer = "path-to-ssh";
      format = "ssh";
      key =
        "ssh-ed25519 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
      signByDefault = true;
    };
  };

  nmt.script = ''
    assertFileExists home-files/.config/git/config
    assertFileContent home-files/.config/git/config ${
      ./git-with-signing-key-id-expected.conf
    }
  '';
}