precommit: Add simple Makefile formatter

tools/precommit/format_makefile.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+
+# author: Ole Schuett
+
+import re
+import sys
+from pathlib import Path
+
+
+def main() -> None:
+    if len(sys.argv) != 2:
+        print("Usage: format_makefile.py <file>")
+        sys.exit(1)
+    makefile = Path(sys.argv[1])
+
+    lines_out = []
+    continuation = False
+    for line in makefile.read_text(encoding="utf8").split("\n"):
+
+        # Remove trailing whitespaces.
+        line = line.rstrip()
+
+        # Detect continued lines.
+        prev_continuation = continuation
+        continuation = line.endswith("\\")
+
+        # Continued lines are indented 8 spaces.
+        if prev_continuation:
+            lines_out.append(" " * 8 + line.strip())
+
+        # Tabbed lines are indented with excatly one tab.
+        elif line.startswith("\t"):
+            lines_out.append("\t" + line.strip())
+
+        # All other lines are not indented.
+        else:
+            lines_out.append(line.strip())
+
+    makefile.write_text("\n".join(lines_out), encoding="utf8")
+
+
+main()
+
+# EOF