Merge branch 'pw/rebase-keep-base-fixes'

"git rebase --keep-base" used to discard the commits that are already cherry-picked to the upstream, even when "keep-base" meant that the base, on top of which the history is being rebuilt, does not yet include these cherry-picked commits. The --keep-base option now implies --reapply-cherry-picks and --no-fork-point options. * pw/rebase-keep-base-fixes: rebase --keep-base: imply --no-fork-point rebase --keep-base: imply --reapply-cherry-picks rebase: factor out branch_base calculation rebase: rename merge_base to branch_base rebase: store orig_head as a commit rebase: be stricter when reading state files containing oids t3416: set $EDITOR in subshell t3416: tighten two tests