Merge branch 'hn/refs-pseudorefs'

Accesses to two pseudorefs have been updated to properly use ref
API.

* hn/refs-pseudorefs:
  sequencer: treat REVERT_HEAD as a pseudo ref
  builtin/commit: suggest update-ref for pseudoref removal
  sequencer: treat CHERRY_PICK_HEAD as a pseudo ref
  refs: make refs_ref_exists public

diff --cc refs.c
Simple merge

diff --cc sequencer.c
Simple merge

diff --cc wt-status.c
Simple merge