In this test, we want to produce several blobs whose first two hex
characters are "17", since we look at this object directory as a proxy
for how many loose objects there are before we need to GC. Use
test_oid_cache to specify strings that will hash to the right values
when turned into blobs.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Reviewed-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>