ci: update Nix installation action

update Nix installation action to v25 and configure trusted keys
and substituters for improved caching and security.

.github/workflows/ci.yml

@@ -47,17 +47,12 @@ jobs:
           key: nix-${{ hashFiles('packages.nix') }}
 
       - name: Install Nix
-        uses: cachix/install-nix-action@v20
+        uses: actions/checkout@v3
+      - uses: cachix/install-nix-action@v25
         with:
-          nix_path: nixpkgs=channel:nixos-unstable
-
-      - name: "Import Nix store cache"
-        if: "steps.nix-cache.outputs.cache-hit == 'true'"
-        run: "nix-store --import < /tmp/nixcache"
-
-      - name: "Export Nix store cache"
-        if: "steps.nix-cache.outputs.cache-hit != 'true'"
-        run: "nix-store --export $(find /nix/store -maxdepth 1 -name '*-*') > /tmp/nixcache"
-
-      - name: Run tests
+          extra_nix_config: |
+            trusted-public-keys = nix.casatta.it:HseKZh7436/vKXfZDBHbhr7wwAkzjLwY5BIq+OOrITg= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+            substituters = https://nix.casatta.it https://cache.nixos.org/
+      - uses: DeterminateSystems/magic-nix-cache-action@v2
+      - name: "test"
         run: nix develop --command make test-${{matrix.test-vector}}

flake.nix

@@ -10,25 +10,41 @@
     # blockstream-electrs: init at 0.4.1 #299761
     # https://github.com/NixOS/nixpkgs/pull/299761/commits/680d27ad847801af781e0a99e4b87ed73965c69a
     nixpkgs2.url = "github:NixOS/nixpkgs/680d27ad847801af781e0a99e4b87ed73965c69a";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-utils.follows = "flake-utils";
+      };
+    };
+    crane = {
+      url = "github:ipetkov/crane";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+      };
+    };
     # lwk: init at wasm_0.6.3 #14bac28
     # https://github.com/Blockstream/lwk/releases/tag/wasm_0.6.3
     lwk-flake = {
       url = "github:blockstream/lwk/14bac284fe712dd6fdbbbe82bda179a2a236b2fa";
       inputs = {
         nixpkgs.follows = "nixpkgs";
         flake-utils.follows = "flake-utils";
+        crane.follows = "crane";
+        rust-overlay.follows = "rust-overlay";
       };
     };
   };
-  outputs = { self, nixpkgs, nixpkgs2, flake-utils, lwk-flake }:
+  outputs = { self, nixpkgs, nixpkgs2, rust-overlay, crane, flake-utils, lwk-flake }:
     flake-utils.lib.eachDefaultSystem
       (system:
         let
+          overlays = [ (import rust-overlay) ];
           pkgs = import nixpkgs {
-            system = system;
+            inherit system overlays;
           };
           pkgs2 = import nixpkgs2 {
-            system = system;
+            inherit system overlays;
           };
           blockstream-electrs = pkgs2.blockstream-electrs.overrideAttrs (oldAttrs: {
             cargoBuildFlags = [ "--features liquid" "--bin electrs" ];