reuse intermediate deno caches

nix/deno/makeDenoShelfSetup.nix

@@ -0,0 +1,19 @@
+{ self }:
+{ pkgs, sharedCache }:
+
+pkgs.writeShellScript "deno-shelf-setup" ''
+  export DENO_DIR=$PWD/.deno_cache
+
+  if [ ! -d "$DENO_DIR" ] || [ "${sharedCache}" -nt "$DENO_DIR/.cache_timestamp" ]; then
+    echo "Setting up shared Deno cache..."
+
+    rm -rf "$DENO_DIR"
+    cp -r "${sharedCache}" "$DENO_DIR"
+    chmod -R u+w "$DENO_DIR"
+
+    touch "$DENO_DIR/.cache_timestamp"
+    echo "Shared Deno cache initialized"
+  else
+    echo "Deno cache is up to date"
+  fi
+''