core.whitespace: add test for diff whitespace error highlighting
core.whitespace: add test for diff whitespace error highlighting

This tests seletive enabling/disabling of whitespace error
highlighting done by colored diff output.

Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git