[O] indentation across multiple source blocks

[Tony Day]

Is there an easy way to preserve indentation for a source block taking
into account previous blocks?  For (a silly) example:


* foo
:PROPERTIES:
:tangle:   yes
:END:
#+begin_src emacs-lisp
  (defun foo ()
#+end_src

#+begin_src emacs-lisp
    (bar)
#+end_src

#+begin_src emacs-lisp
  )
#+end_src

Any help much appreciated.

Tony