Run clang tidy on diff with CI

Added a script for CI execution. This script is not intended for local
user execution due to the following reasons:

1. `clang-tidy-diff.py` supports exit with a failure code when there are
   errors from version 17 onward. (The exact version is uncertain. For
   more details, please refer to
   llvm/llvm-project#65000.)
2. `bear` has different command line interfaces between version <= 2.4.x
    and onward. (For more details, please refer to
    https://github.com/rizsotto/Bear?tab=readme-ov-file#how-to-use.)

The script may not work if any of these issues occur.
In the CI environment, we ensure that the versions of these dependencies
are new enough.

.github/workflows/ci.yml

@@ -17,6 +17,11 @@ jobs:
         run: |
           sudo apt-get install -q -y clang-format
           scripts/check-format.sh
+      - name: static checks
+        run: |
+          sudo apt-get install -q -y bear clang-tidy-17
+          scripts/check-tidy.sh
+
   test:
     runs-on: ubuntu-22.04
     strategy:

.gitignore

@@ -58,3 +58,6 @@ venv.bak/
 
 # VS Code configs
 .vscode
+
+# Compilation database
+compile_commands.json

scripts/check-tidy.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env sh
+
+#
+# Runs clang-tidy-diff.py on the diff between main and HEAD.
+#
+
+set -eu
+
+command -v bear >/dev/null 2>&1 || (
+  echo "error: bear is required to generate compile_commands.json; see https://github.com/rizsotto/Bear"
+  exit 1
+)
+
+# number of jobs to run
+NPROCS=1
+# Find available processor numbers based on different OS.
+OS="$(uname -s)"
+case $OS in
+'Linux')
+  NPROCS="$(grep -c ^processor /proc/cpuinfo)"
+  ;;
+'Darwin')
+  NPROCS="$(sysctl -n hw.ncpu)"
+  ;;
+esac
+
+# Run a clean build to generate compile_commands.json.
+make clean
+bear make -j"${NPROCS}"
+git diff -U0 main..HEAD | clang-tidy-diff -p1 -j"${NPROCS}"