chevex/yargs — pull request #70 by ashi009 (2014-11-23 03:46:34+00:00)
Title: fix #69: Allow explicit `default: undefined` for flags

It’s possible to know if the user not set certain flags, after set `default: undefined` for that field.

_This change is very unlikely to break anything, and it behaves the same when not set `default` or set it `true/false`._