Merge branch 'np/pack'

Merge branch 'np/pack'

* np/pack: (27 commits)
  document --index-version for index-pack and pack-objects
  pack-objects: remove obsolete comments
  pack-objects: better check_object() performances
  add get_size_from_delta()
  pack-objects: make in_pack_header_size a variable of its own
  pack-objects: get rid of create_final_object_list()
  pack-objects: get rid of reuse_cached_pack
  pack-objects: clean up list sorting
  pack-objects: rework check_delta_limit usage
  pack-objects: equal objects in size should delta against newer objects
  pack-objects: optimize preferred base handling a bit
  clean up add_object_entry()
  tests for various pack index features
  use test-genrandom in tests instead of /dev/urandom
  simple random data generator for tests
  validate reused pack data with CRC when possible
  allow forcing index v2 and 64-bit offset treshold
  pack-redundant.c: learn about index v2
  show-index.c: learn about index v2
  sha1_file.c: learn about index version 2
  ...