#4 OptionGroupRequirement.ExactlyOne is not processe correctly.

[Wolfgang Kleinschmit]

In file ($Id: CommandLineParser.cs 19 2007-08-15 13:14:32Z palotas $) line 610 should read:
if (optionCount != 1)
instead of
if (optionCount == 0)

the latter would mean something like OptionGroupRequirement.None which doesn't exist.