Move a helper script (indent_begin_end.py) to contrib dir

contrib/indent_begin_end.py

@@ -0,0 +1,15 @@
+#!/usr/bin/env python
+
+import sys
+
+indent = b""
+
+with open(sys.argv[1], 'rb') as fin:
+    with open(sys.argv[2], 'wb') as fout:
+        for line in fin:
+            if line.endswith(b"end\r\n"):
+                indent = indent[:-2]
+            fout.write(indent)
+            fout.write(line)
+            if line.endswith(b"begin\r\n"):
+                indent = indent + b"  "