enable flakes thru env var

.woodpecker/cd.yaml

@@ -13,7 +13,17 @@ steps:
         mkdir -p ~/.ssh
         echo "$CD_SSH_KEY" > ~/.ssh/id_ed25519
         chmod 600 ~/.ssh/id_ed25519
-      - nix-shell --extra-experimental-features 'nix-command flakes' --run 'eval "$(ssh-agent -s)" && ssh-add ~/.ssh/id_ed25519 && ssh-agent -s && SHELL=$(which bash) nixops4 apply -v default'
+      - |
+        NIX_CONFIG="
+          experimental-features = nix-command flakes
+        " nix-shell --run 'eval "$(ssh-agent -s)" && ssh-add ~/.ssh/id_ed25519 && SHELL=$(which bash) nixops4 apply -v default'
+        # --extra-experimental-features 'nix-command flakes'
+          # substituters = https://cache.nixos.org/
+          # system-features = nixos-test benchmark big-parallel kvm
+          # trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+          # trusted-substituters =
+          # trusted-users = root @wheel
+          # extra-sandbox-paths =
     environment:
       CD_SSH_KEY:
         from_secret: cd_ssh_key