Ensure that a test is run in the trash directory

Exit with error if cd into the "trash directory" failed (error
already reported, so just exit).
Signed-off-by: NAlex Riesen <raa.lkml@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -419,7 +419,7 @@ rm -fr "$test" || {
 }
 
 test_create_repo "$test"
-cd "$test"
+cd "$test" || exit 1
 
 this_test=$(expr "./$0" : '.*/\(t[0-9]*\)-[^/]*$')
 for skp in $GIT_SKIP_TESTS