Merge branch 'ra/rebase-i-more-options'

"git rebase -i" learned a few options that are known by "git rebase" proper. * ra/rebase-i-more-options: rebase -i: finishing touches to --reset-author-date rebase: add --reset-author-date rebase -i: support --ignore-date sequencer: rename amend_author to author_to_rename rebase -i: support --committer-date-is-author-date sequencer: allow callers of read_author_script() to ignore fields rebase -i: add --ignore-whitespace flag