#2 Feature req: Dependencies between arguments

[Toxic]

A feature request:

I'd like to be able to specify dependencies between arguments.
For instance,

1) Only one of the two arguments will be accepted
E.g., flags --client and --server should not allowed at the same time

The following should generate an error:
java myProgram --server --client

2) If one parameter is given, it must take another
E.q., The --server argument requires the existence of the --port argument.

java myProgram --server --port 10

Otherwise, thanks for a great parser!