JANITORIAL: add pre-commit yaml with clang-tidy

You can opt-in by install pre-commit, `pip install --upgrade pre-commit`,
then run `pre-commit install` in scummvm directory.

.clang-format

@@ -19,5 +19,5 @@
     SpacesInAngles: false,
     SpacesInParentheses: false,
     SpacesInSquareBrackets: false,
-    Standard: c++03,
+    Standard: c++11,
 }

.pre-commit-config.yaml

@@ -0,0 +1,18 @@
+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v6.0.0
+  hooks:
+    - id: check-yaml
+    - id: end-of-file-fixer
+    - id: trailing-whitespace
+- repo: https://github.com/pre-commit/mirrors-clang-format
+  rev: v21.1.2
+  hooks:
+  - id: clang-format
+- repo: local
+  hooks:
+    - id: check-commit-msg
+      name: check-commit-msg
+      language: python
+      entry: devtools/check-commit-msg.py
+      stages: [ commit-msg ]

devtools/check-commit-msg.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+
+import sys
+import os
+import re
+from argparse import ArgumentParser
+
+parser = ArgumentParser(description="SCUMMVM check commit message hook")
+parser.add_argument("message")
+args = parser.parse_args()
+
+with open(args.message, "rt") as f:
+    text = f.read()
+
+MESSAGE_FORMAT = re.compile(r"[A-Z_]+:")
+
+if MESSAGE_FORMAT.match(text):
+	sys.exit(0)
+
+print("Please start your commit message with subsystem or engine name written in CAPS", file=sys.stderr)
+print("See https://wiki.scummvm.org/index.php/Commit_Guidelines", file=sys.stderr)
+print("Your original message follows:\n\n", text)
+sys.exit(1)