fix some issues with rust template's rename

rust/flake.nix

@@ -59,11 +59,16 @@
           runtimeInputs = [
             pkgs.fd
             pkgs.coreutils
+            pkgs.nixFlakes
+            pkgs.jq
           ];
           text = ''
-            stat nix/packages/change-my-name.nix 2>/dev/null >/dev/null || echo "Can only be done once!"
             newName="$1"
-            pushd "$(git rev-parse --show-toplevel)"
+            pushd "$(nix flake metadata --json 2>/dev/null | jq .original.path -r)"
+            # This is only used to prevent the literal name from appearing here, as the rename would find it!
+            oldName=$(echo 'change_my_name' | sed 's/_/-/g')
+            stat "nix/packages/$oldName.nix" 2>/dev/null >/dev/null || echo -e "\033[31mCan only be done once\033[0m"
+            stat "nix/packages/$oldName.nix" 2>/dev/null >/dev/null || exit 1
             fd --type f --exec sed "s/change-my-name/$newName/g" -i '{}'
             mv nix/packages/change-my-name.nix "nix/packages/$newName.nix"
           '';