This commit takes advantage of Ævar Arnfjörð Bjarmason's recent change
to test_expect_code (test-lib: make test_expect_code a test command) to
simplify several testcases.
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>