Inheritable flags. (Feature Request)

[codefriar]

I'd really love a way to have child commands inherit flags from their parent.

For instance:

myCli
parentCommand
-c flag
fooCommand understands -c, even though it's defined on parentCommand.

This would be useful for defining common command line params to an entire 'namespace'.
Another example: a 'config' namespace / parent command has a common flag -f for config file that config set and config get could both use.