rubygems/rubygems — pull request #578 by havenwood (2013-06-27 03:35:57+00:00)
Title: Raise an error if more than one gem name is specified with `gem list`.

Resolve #572 by adding and using a #get_only_one_optional_argument method that is quite similar to #get_one_optional_argument but raises a Gem::CommandLineError exception if more than one gem name is specified.