add ci to check cmake formatting

.github/workflows/check-formatting.yml

@@ -0,0 +1,14 @@
+name: Check Formatting
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+jobs:
+  check-formatting:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - run: pip3 install gersemi
+      - run: ./extras/formatting.sh --check-only

extras/formatting.sh

@@ -0,0 +1,66 @@
+#!/usr/bin/env bash
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
+cd "$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel)" || exit 1
+
+check_only=0
+
+while [[ "$#" -gt 0 ]]; do
+  case $1 in
+  -h | --help) help=1 ;;
+  --check-only) check_only=1 ;;
+  esac
+  shift
+done
+
+if [ "$help" ]; then
+  me=$(basename "$0")
+  cat <<EOF
+$me: Format or check formatting of files in this repo
+
+Usage: $me [--check-only]
+
+Options:
+    --check-only     Check formatting without modifying files
+EOF
+  exit 0
+fi
+
+require_bin() {
+  if ! command -v "$1" &>/dev/null; then
+    echo "This script needs $1, but it isn't in \$PATH"
+    missing_bin=1
+  fi
+}
+
+require_bin "git"
+require_bin "gersemi"
+
+if [ "$missing_bin" ]; then
+  exit 1
+fi
+
+exit_code=0
+
+cmake_formatting() {
+  readarray -t files < <(git ls-files '*.cmake' '**/CMakeLists.txt')
+
+  common_args=(
+    # turn on warning when this is fixed https://github.com/BlankSpruce/gersemi/issues/39
+    --no-warn-about-unknown-commands
+    --definitions "${files[@]}"
+  )
+
+  if [ "$check_only" -eq 1 ]; then
+    gersemi "${common_args[@]}" --diff --color "${files[@]}"
+    gersemi "${common_args[@]}" --check "${files[@]}" || exit_code=1
+  else
+    gersemi "${common_args[@]}" --in-place "${files[@]}"
+  fi
+}
+
+cmake_formatting
+
+exit $exit_code