Move CI-only check-format script to .github/

.github/scripts/check-format.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env sh
+
+# SPDX-License-Identifier: MIT
+
+clang-format --version
+
+find . -type f -iname '*.[ch]pp' -exec clang-format -i {} +
+
+if ! git diff-index --quiet HEAD --; then
+	echo 'Unformatted files:'
+	git diff-index --name-only HEAD --
+	echo
+	git diff HEAD --
+	exit 1
+fi

.github/workflows/check-format.yml

@@ -8,7 +8,7 @@ env:
   CLICOLOR_FORCE: 1
 
 jobs:
-  checkformat:
+  check-format:
     runs-on: ubuntu-slim
     steps:
       - name: Checkout repo
@@ -18,4 +18,4 @@ jobs:
           sudo apt install -Uyq clang-format
       - name: Check format
         run: |
-          contrib/checkformat.sh
+          .github/scripts/check-format.sh