* add lang-agnostic tests
  * for DocoptLanguageError
  * for '-' and '--'
* maybe: arbitrary number of short/long aliases for options
* default values for positinal arguments like:
  <path>  Path to files. [default ./]

Unsupported syntax found in git:
--exec-path[=<path>]
-u<mode>
[(-c | -C | --fixup | --squash) <commit>]
