Merge branch 'maint'

* maint:
  Extend parse-options test suite
  api-parse-options.txt: Introduce documentation for parse options API
  parse-options.c: fix documentation syntax of optional arguments
  api-builtin.txt: update and fix typo

diff --cc parse-options.c
Simple merge

diff --cc t/t1502-rev-parse-parseopt.sh
Simple merge