How to do a git diff on moved/renamed file?

You need to use -M to let git autodetect the moved file when diffing. Using just git diff as knittl mentioned does not work for me.

So simply: git diff -M should do it.

The documentation for this switch is:

-M[<n>], --find-renames[=<n>]
       Detect renames. If n is specified, it is a threshold on the similarity index 
       (i.e. amount of addition/deletions compared to the file’s size). For example, 
       -M90% means git should consider a delete/add pair to be a rename if more than
       90% of the file hasn’t changed.