Merge branch 'pw/rebase-drop-notes-with-commit'

The rebase post-rewrite notes-copying logic has been corrected.  When
a commit is dropped during rebase (e.g., because its changes are
already upstream), it is no longer recorded as rewritten, preventing
its notes from being copied to an unrelated commit.

* pw/rebase-drop-notes-with-commit:
  sequencer: do not record dropped commits as rewritten
  sequencer: use an enum to represent result of picking a commit
  sequencer: simplify pick_one_commit()
  sequencer: remove unnecessary condition in pick_one_commit()
  sequencer: simplify handling of fixup with conflicts
  sequencer: remove unnecessary "or" in pick_one_commit()
  sequencer: never reschedule on failed commit
  sequencer: be more careful with external merge
  t3400: restore coverage for note copying with apply backend

diff --cc sequencer.c
Simple merge

diff --cc t/t3400-rebase.sh
Simple merge

diff --cc t/t3404-rebase-interactive.sh
Simple merge

diff --cc t/t5407-post-rewrite-hook.sh
Simple merge