We can apply patches to existing packages using [[overlays]]:
```nix
final: prev {
  nova = prev.nova.overrideAttrs (old: {
	  patches = (old.patches or []) ++ [
		  prev.fetchpatch {
			url = "https://github.com/owner/repo/commit/hash.patch";
		    hash = "somehash";
		})
		./relative.patch
	  ]
  })
}
```