The write_commit_graph() method is too complex, so we are
extracting helper functions one by one.
Extract fill_oids_from_all_packs() that reads all pack-files
for commits and fills the oid list in the context.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>