test-split: split now ignores diff.* settings
From 66399f2e92aa: "It is assumed by the author that the `[diff]` section is
primarily for *viewing* diffs, and that it is unlikely what people intend when
attempting to commit or revert."
test-drop.t
test-inhibit.t
test-simple4server.t
tests/test-simple4server-bundle2.t