Merge branch 'en/ort-perf-batch-12'

More fix-ups and optimization to "merge -sort".

* en/ort-perf-batch-12:
  merge-ort: miscellaneous touch-ups
  Fix various issues found in comments
  diffcore-rename: avoid unnecessary strdup'ing in break_idx
  merge-ort: replace string_list_df_name_compare with faster alternative

diff --cc diffcore-rename.c
Simple merge

diff --cc merge-ort.c
Simple merge

diff --cc t/t6423-merge-rename-directories.sh
Simple merge