Merge branch 'en/ort-perf-batch-14' into next

Further optimization on "merge -sort" backend.

* en/ort-perf-batch-14:
  merge-ort: restart merge with cached renames to reduce process entry cost
  merge-ort: avoid recursing into directories when we don't need to
  merge-ort: defer recursing into directories when merge base is matched
  merge-ort: add a handle_deferred_entries() helper function
  merge-ort: add data structures for allowable trivial directory resolves
  merge-ort: add some more explanations in collect_merge_info_callback()
  merge-ort: resolve paths early when we have sufficient information

Author: gitster