{
  pkgs,
  lib,
  user,
  ...
}: {
  programs.ssh = {
    enable = true;
    includes = [
      (lib.mkIf pkgs.stdenv.hostPlatform.isLinux "/home/${user}/.ssh/config_external")
      (lib.mkIf pkgs.stdenv.hostPlatform.isDarwin "/Users/${user}/.ssh/config_external")
    ];
    matchBlocks = {
      "github.com" = {
        identitiesOnly = true;
        identityFile = [
          (lib.mkIf pkgs.stdenv.hostPlatform.isLinux "/home/${user}/.ssh/id_ed25519")
          (lib.mkIf pkgs.stdenv.hostPlatform.isDarwin "/Users/${user}/.ssh/id_ed25519")
        ];
      };
    };
  };
}