[gentoo-user] Seeing USE flag descriptions for a package

[Stroller]

Hi there,

When I install a new package I run `emerge -pv foo` to look at the  
USEs it supports.  In the past I have looked these up just by  
grepping, e.g.:

   $ grep foo /usr/portage/profiles/use.*
   /usr/portage/profiles/use.desc:foomaticdb - Adds support for the  
foomatic printing driver database
   $

However I have recently learned to use `euse -i foo` instead. This is  
much more convienient than grepping because one can use the Bash  
history: up-arrow, ctrl-w to delete the last word & type in or paste  
the name of the next USE to check it. However this is clumsy when you  
have a package (like mplayer) with many USE flags.

What I would like to be able to do is:

   $ $magicusecommand category/package
   doc - Install HTML wxWidgets docs and wxpython API reference.
   examples - Install interactive demo module browser and sample  
applets.
   samba - Adds support for SAMBA (Windows File and Printer sharing)
   $

The command should print out the descriptions for ALL the USE flags  
supported by the category/package, but only for that category/package.  
Ideally it should show if they're currently enabled or not.

I can't be the only person to desire this feature - surely there must  
be a package or command do do this. I can't find this in `man portage`  
as an advanced version of `emerge -pv package`. Can anyone tell me  
what $magicusecommand is called, please?

Thanks in advance,

Stroller.