how to create a diff in old file new file format (for code reviews)

Hi,

I am trying to create a diff such that the original file (entire file) is saved something like file1.h.old and the new modified file as file1.h.new. I have read the various options for git-diff* tools but could not find one such utility. All I get is the removals and additions as a diff. Does anyone know how to create one with the help the available git utils? The only method that I can think of is to do everything manually. Any help w.r.t. this is really appreciated. Thanks in advance.