Merge branch 'pw/sequence-rerere-autoupdate' into maint

Commands like "git rebase" accepted the --rerere-autoupdate option
from the command line, but did not always use it.  This has been
fixed.

* pw/sequence-rerere-autoupdate:
  cherry-pick/revert: reject --rerere-autoupdate when continuing
  cherry-pick/revert: remember --rerere-autoupdate
  t3504: use test_commit
  rebase -i: honor --rerere-autoupdate
  rebase: honor --rerere-autoupdate
  am: remember --rerere-autoupdate setting