Merge branch 'jk/push-progress'

Merge branch 'jk/push-progress'

"git push" and "git clone" learned to give better progress meters
to the end user who is waiting on the terminal.

* jk/push-progress:
  receive-pack: send keepalives during quiet periods
  receive-pack: turn on connectivity progress
  receive-pack: relay connectivity errors to sideband
  receive-pack: turn on index-pack resolving progress
  index-pack: add flag for showing delta-resolution progress
  clone: use a real progress meter for connectivity check
  check_connected: add progress flag
  check_connected: relay errors to alternate descriptor
  check_everything_connected: use a struct with named options
  check_everything_connected: convert to argv_array
  rev-list: add optional progress reporting
  check_everything_connected: always pass --quiet to rev-list