(deltified representation)
n-byte type and length (3-bit type, (n-1)*7+4-bit length)
- 20-byte base object name
+ 20-byte base object name if OBJ_REF_DELTA or a negative relative
+ offset from the delta object's position in the pack if this
+ is an OBJ_OFS_DELTA object
compressed delta data
Observation: length of each object is encoded in a variable