Merge branch 'nd/parse-options-aliases'

Merge branch 'nd/parse-options-aliases'

Attempt to use an abbreviated option in "git clone --recurs" is
responded by a request to disambiguate between --recursive and
--recurse-submodules, which is bad because these two are synonyms.
The parse-options API has been extended to define such synonyms
more easily and not produce an unnecessary failure.

* nd/parse-options-aliases:
  parse-options: don't emit "ambiguous option" for aliases