Merge branch 'nd/diff-parseopt-3'

Third batch to teach the diff machinery to use the parse-options API. * nd/diff-parseopt-3: diff-parseopt: convert --submodule diff-parseopt: convert --ignore-submodules diff-parseopt: convert --textconv diff-parseopt: convert --ext-diff diff-parseopt: convert --quiet diff-parseopt: convert --exit-code diff-parseopt: convert --color-words diff-parseopt: convert --word-diff-regex diff-parseopt: convert --word-diff diff-parseopt: convert --[no-]color diff-parseopt: convert --[no-]follow diff-parseopt: convert -R diff-parseopt: convert -a|--text diff-parseopt: convert --full-index diff-parseopt: convert --binary diff-parseopt: convert --anchored diff-parseopt: convert --diff-algorithm diff-parseopt: convert --histogram diff-parseopt: convert --patience diff-parseopt: convert --[no-]indent-heuristic