Merge branch 'np/index-pack'

Merge branch 'np/index-pack'

* np/index-pack:
  remove .keep pack lock files when done with refs update
  have index-pack create .keep file more carefully
  improve fetch-pack's handling of kept packs
  git-fetch can use both --thin and --keep with fetch-pack now
  Teach receive-pack how to keep pack files based on object count.
  Allow pack header preprocessing before unpack-objects/index-pack.
  Remove unused variable in receive-pack.
  Revert "send-pack --keep: do not explode into loose objects on the receiving end."
  missing small substitution
  Teach git-index-pack how to keep a pack file.
  Only repack active packs by skipping over kept packs.
  Allow short pack names to git-pack-objects --unpacked=.
  send-pack --keep: do not explode into loose objects on the receiving end.
  index-pack: minor fixes to comment and function name
  enhance clone and fetch -k experience
  mimic unpack-objects when --stdin is used with index-pack
  add progress status to index-pack
  make index-pack able to complete thin packs.
  enable index-pack streaming capability