Merge branch 'rs/parse-options-with-keep-unknown-abbrev-fix'

"git diff --no-rename A B" did not disable rename detection but did not trigger an error from the command line parser. * rs/parse-options-with-keep-unknown-abbrev-fix: parse-options: simplify positivation handling parse-options: fully disable option abbreviation with PARSE_OPT_KEEP_UNKNOWN