Add CI check for fomatting

.github/workflows/fmt-check.yml

@@ -0,0 +1,29 @@
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - "**.nix"
+      - "**.lock"
+      - ".github/workflows/nix-build.yml"
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v26
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - run: |
+          nix buld nixpkgs#clang-tools
+          find . -type f -name "*.c" -or -name "*.h" \
+            | xargs -i ./result/bin/clang-format -i {}
+          out=out=$(git status  \
+              | grep "modified" \
+              | cut -d ":" -f 2 \
+              | sort            \
+              | xargs           \
+              | tee /dev/stderr \
+              | wc -c)
+          [ $out -ge 1 ] && exit 1 || exit 0

flake.nix

@@ -25,6 +25,7 @@
           bear
           python3Packages.compiledb
           gcovr
+          clang-tools
         ];
       };