wip: test hashing flake.lock file

.forgejo/workflows/check.yml

@@ -17,18 +17,23 @@ jobs:
             substituters = https://cache.nixos.org/ https://nix-community.cachix.org
             trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=
             keep-outputs = true
+      - name: Calculate flake.lock hash
+        id: flake-lock-hash
+        run: |
+          echo "hash=$(md5sum flake.lock)" >> $GITHUB_OUTPUT     
       - name: Restore and cache Nix store
         uses: https://github.com/nix-community/cache-nix-action@v4
+        id: nix-store-cache # use this to check for `cache-hit` (`steps.nix-store-cache.outputs.cache-hit != 'true'`)
         with:
-          key: cache-x86_64-linux-nix-store
+          key: cache-x86_64-linux-nix-store-${{ steps.flake-lock-hash.outputs.hash }}
           restore-keys: |
-            cache-x86_64-linux-
+            cache-x86_64-linux-nix-store-
 
           gc-linux: true
           gc-max-store-size-linux: 10000000000
 
           purge-caches: true
-          purge-key: cache-x86_64-linux-
+          purge-key: cache-x86_64-linux-nix-store-
           purge-created: true
           purge-created-max-age: 42
       - name: Check out repository code