Merge branch 'ws/rebase-p'

Code clean-up. * ws/rebase-p: rebase: remove merges_option and a blank line rebase: remove unused code paths from git_rebase__interactive__preserve_merges rebase: remove unused code paths from git_rebase__interactive rebase: add and use git_rebase__interactive__preserve_merges rebase: extract functions out of git_rebase__interactive rebase: reindent function git_rebase__interactive rebase: update invocation of rebase dot-sourced scripts rebase-interactive: simplify pick_on_preserving_merges