Support for different help messages for same argument in different constructors

I don't know if it's possible, but something like:

```
data Example1 =
Example1
{ foo :: Int "Documentation for the foo flag in Example1"
, bar :: Double "Documentation for the bar flag in Example1"
}
| Example2
{ foo :: Int "Documentation for the foo flag in Example2"
, bar :: Double "Documentation for the bar flag in Example2"
}

deriving (Generic, Show)
```
Probably requiring some type of record fields. This feature would be quite useful in that you could have a program with multiple entry points with the same arguments, such as `input` but take in different formats.