Merge branch 'en/ort-conflict-handling' into en/merge-ort-perf

* en/ort-conflict-handling:
  merge-ort: add handling for different types of files at same path
  merge-ort: copy find_first_merges() implementation from merge-recursive.c
  merge-ort: implement format_commit()
  merge-ort: copy and adapt merge_submodule() from merge-recursive.c
  merge-ort: copy and adapt merge_3way() from merge-recursive.c
  merge-ort: flesh out implementation of handle_content_merge()
  merge-ort: handle book-keeping around two- and three-way content merge
  merge-ort: implement unique_path() helper
  merge-ort: handle directory/file conflicts that remain
  merge-ort: handle D/F conflict where directory disappears due to merge

Author: gitster