like this:
```
  src = fetchFromGitHub {
    owner = "Unvanquished";
    repo = "Unvanquished";
    rev = "v${version}";
    sha256 = "5273bbdc6b449e91c4ab835dd8e6b1cf6a97679006fbfceeb1e4dc8be97d8f81";
  }; 
```