Follow good practice and add main() to split.py

split.py

@@ -10,6 +10,8 @@ border = (
     "// ----------------------------------------------------------------------------"
 )
 
+
+def main():
     args_parser = argparse.ArgumentParser(description=__doc__)
     args_parser.add_argument(
         "-e",
@@ -69,3 +71,7 @@ if do_split:
         print("Wrote {} and {}".format(h_out, cc_out))
     else:
         print("{} and {} are up to date".format(h_out, cc_out))
+
+
+if __name__ == "__main__":
+    main()