org-babel-pre-tangle-hook is a variable defined in `ob-tangle.el'.
Its value is
(save-buffer)
This variable may be risky if used as a file-local variable.
Documentation:
Hook run at the beginning of `org-babel-tangle'.
You can customize this variable.
This variable was introduced, or its default value was changed, in
version 24.1 of Emacs.