chore: add treefmt config for nix files

* add a ci job that run `treefmt`
* make it `nix fmt` default formatter
* add dumb simple `pre-commit` and `editorconfig`

Author: yvan-sraka

.editorconfig

@@ -0,0 +1,12 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*.nix]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true

.github/workflows/treefmt.yml

@@ -0,0 +1,15 @@
+name: treefmt
+on:
+    pull_request:
+    push:
+        branches: develop
+jobs:
+    formatter:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v4
+            - uses: cachix/install-nix-action@v31
+              with:
+                  nix_path: nixpkgs=channel:nixos-unstable
+            - name: treefmt
+              run: nix-shell -p treefmt nixpkgs-fmt --run "treefmt --ci"

.gitignore

@@ -17,7 +17,7 @@ __pycache__/
 result*
 .env-local
 .history
-
+.envrc
 
 #IDE
 .idea/

.pre-commit-config.yaml

@@ -0,0 +1,8 @@
+repos:
+  - repo: local
+    hooks:
+      - id: treefmt
+        name: treefmt
+        entry: treefmt
+        language: system
+        types: [file]

flake.nix

@@ -1413,6 +1413,8 @@
             trigger-nix-build = mkApp "trigger-nix-build" "trigger-nix-build";
           };
 
+        formatter = pkgs.treefmt;
+
         # 'devShells.default' lists the set of packages that are included in the
         # ambient $PATH environment when you run 'nix develop'. This is useful
         # for development and puts many convenient devtools instantly within
@@ -1456,7 +1458,10 @@
                 basePackages.run-testinfra
                 basePackages.cleanup-ami
                 dbmate
+                formatter # treefmt
+                nixpkgs-fmt
                 nushell
+                pre-commit
                 pythonEnv
                 nix-fast-build
               ];

treefmt.toml

@@ -0,0 +1,5 @@
+# One CLI to format the code tree - https://github.com/numtide/treefmt
+
+[formatter.nix]
+command = "nixpkgs-fmt"
+includes = ["*.nix"]