Rename the "diff-lib" to "lib-diff". With this rename and preceding
commits there is no remaining t/*lib* which doesn't follow the
convention of being called t/lib-*.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Ævar Arnfjörð Bjarmason