chores: Add spaces to tabs fix for mixed

.pre-commit-config.yaml

@@ -28,3 +28,10 @@ repos:
   - id: mixed-line-ending
     args: [--fix,lf]
   - id: trailing-whitespace
+- repo: local
+  hooks:
+    - id: indent-fix
+      name: Convert indentation spaces to tabs
+      entry: python3 misc/spaces_to_tabs.py
+      language: system
+      files: \.(cc|h)$

misc/spaces_to_tabs.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+
+import re
+import sys
+from pathlib import Path
+
+changed = False
+
+for filename in sys.argv[1:]:
+    path = Path(filename)
+
+    try:
+        text = path.read_text()
+    except UnicodeDecodeError:
+        continue
+
+    # Determine whether this file uses tabs for indentation.
+    uses_tabs = any(
+        re.match(r"^\t+", line)
+        for line in text.splitlines()
+    )
+
+    if not uses_tabs:
+        continue
+
+    new_text = re.sub(
+        r"^(?: {4})+",
+        lambda m: "\t" * (len(m.group()) // 4),
+        text,
+        flags=re.MULTILINE,
+    )
+
+    if new_text != text:
+        path.write_text(new_text)
+        changed = True
+        print(f"Converted indentation to tabs: {filename}")
+
+sys.exit(1 if changed else 0)