Merge branch 'nh/empty-rebase'

"git rebase" learned to optionally keep commits that do not introduce
any change in the original history.

By Neil Horman
* nh/empty-rebase:
  git-rebase: add keep_empty flag
  git-cherry-pick: Add test to validate new options
  git-cherry-pick: Add keep-redundant-commits option
  git-cherry-pick: add allow-empty option

diff --cc builtin/revert.c
Simple merge

diff --cc git-rebase--interactive.sh
Simple merge

diff --cc sequencer.c
Simple merge