[Orgmode] Novice questions about using git for personal data files

[Alan E. Davis]

I followed the steps outlined in the worg tutorial about using git to keep track of changes to one's own org data tree. 

I still don't understand: how does one go about recovering an earlier version of a file that has been corrupted?  Is there a good tutorial on this aspect of using git?  I really like this idea, especially since I have several times bodged an org-mode file by foolishly doing this:
   C-x C-T * 

and making other importune mistakes.  

Thank you,

 
-- 
Alan 

It is undesirable to believe a proposition when 
there is no ground whatsoever for supposing it is true.
  -- Bertrand Russell