Merge branch 'rs/parse-options-with-keep-unknown-abbrev-fix' into maint-2.43

"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

diff --cc parse-options.c
Simple merge

diff --cc t/t4013-diff-various.sh
Simple merge