In Git versions 1.8.5 and newer, you can do this using the --diff-filter option and specifying “d” (lowercase) to tell it to exclude deleted files.
$ git diff --diff-filter=d
In Git versions older than 1.8.5, you can do this with the --diff-filter option and specifying all but the “D” (deleted) criteria:
$ git diff --diff-filter=ACMRTUXB