The code for reading certain pack v2 offsets had a hard-coded 5
representing the number of uint32_t words that we needed to skip over.
Specify this value in terms of a value from the_hash_algo.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>