formatting: add pre-commit hook to dev shell

flake-parts/formatting.nix

@@ -3,9 +3,10 @@
 , ...
 }: {
   imports = [
+    inputs.pre-commit-hooks-nix.flakeModule
     inputs.treefmt-nix.flakeModule
   ];
-  perSystem = { pkgs, ... }: {
+  perSystem = { pkgs, config, ... }: {
     treefmt.projectRootFile = "flake.nix";
     treefmt.flakeCheck = true;
     treefmt.flakeFormatter = true;
@@ -36,5 +37,16 @@
       ];
       includes = [ "*.py" ];
     };
+
+    # activated in devShells via inputsFrom = [config.pre-commit.devShell];
+    pre-commit.settings.hooks.format-all = {
+      name = "format-all";
+      enable = true;
+      pass_filenames = true;
+      entry = toString (pkgs.writeScript "treefmt" ''
+        #!${pkgs.bash}/bin/bash
+        ${config.treefmt.build.wrapper}/bin/treefmt --clear-cache --fail-on-change "$@"
+      '');
+    };
   };
 }