* jk/ort-unused-parameter-cleanups:
merge-ort: lowercase a few error messages
merge-ort: drop unused "opt" parameter from merge_check_renames_reusable()
merge-ort: drop unused parameters from detect_and_process_renames()
merge-ort: stop passing "opt" to read_oid_strbuf()
merge-ort: drop custom err() function