fix: use unwrapped nix-index, patch it for https (for now)

flake.nix

@@ -6,6 +6,10 @@
   outputs = { self, nixpkgs }:
     {
       overlays.default = final: prev: {
+        nix-index-unwrapped = prev.nix-index-unwrapped.overrideAttrs(old: {
+          patches = [ ./nix-index-https.patch ];
+        });
+
         nixos-channel-native-programs = with final; stdenv.mkDerivation {
           name = "nixos-channel-native-programs";
           buildInputs = [
@@ -48,7 +52,7 @@
               brotli
               jq
               nixos-channel-native-programs
-              nix-index
+              nix-index-unwrapped
             ];
 
           buildCommand = ''

nix-index-https.patch

@@ -0,0 +1,10 @@
+diff --git a/src/lib.rs b/src/lib.rs
+index 4393e4b..4a84fc0 100644
+--- a/src/lib.rs
++++ b/src/lib.rs
+@@ -23,4 +23,4 @@ pub mod workset;
+ /// The URL of the binary cache that we use to fetch file listings and references.
+ ///
+ /// Hardcoded for now, but may be made a configurable option in the future.
+-pub const CACHE_URL: &str = "http://cache.nixos.org";
++pub const CACHE_URL: &str = "https://cache.nixos.org";