Merge branch 'js/rebase-i-redo-exec'

Merge branch 'js/rebase-i-redo-exec'

"git rebase -i" learned to re-execute a command given with 'exec'
to run after it failed the last time.

* js/rebase-i-redo-exec:
  rebase: introduce a shortcut for --reschedule-failed-exec
  rebase: add a config option to default to --reschedule-failed-exec
  rebase: introduce --reschedule-failed-exec