Merge branch 'en/merge-recursive'

* en/merge-recursive: (41 commits)
  t6022: Use -eq not = to test output of wc -l
  merge-recursive:make_room_for_directories - work around dumb compilers
  merge-recursive: Remove redundant path clearing for D/F conflicts
  merge-recursive: Make room for directories in D/F conflicts
  handle_delete_modify(): Check whether D/F conflicts are still present
  merge_content(): Check whether D/F conflicts are still present
  conflict_rename_rename_1to2(): Fix checks for presence of D/F conflicts
  conflict_rename_delete(): Check whether D/F conflicts are still present
  merge-recursive: Delay modify/delete conflicts if D/F conflict present
  merge-recursive: Delay content merging for renames
  merge-recursive: Delay handling of rename/delete conflicts
  merge-recursive: Move handling of double rename of one file to other file
  merge-recursive: Move handling of double rename of one file to two
  merge-recursive: Avoid doubly merging rename/add conflict contents
  merge-recursive: Update merge_content() call signature
  merge-recursive: Update conflict_rename_rename_1to2() call signature
  merge-recursive: Structure process_df_entry() to handle more cases
  merge-recursive: Have process_entry() skip D/F or rename entries
  merge-recursive: New function to assist resolving renames in-core only
  merge-recursive: New data structures for deferring of D/F conflicts
  ...

Conflicts:
	t/t6020-merge-df.sh
	t/t6036-recursive-corner-cases.sh