[gentoo-user] Same version in portage and overlay, how to mask?

[Alan McKinnon]

If I have identically named packages with the *same* version number in the 
portage tree and in an overlay, how do I mask the overlay version without 
deleting the overlay?

I have kde-testing enabled to get koffice:2, but some packages conflict with 
portage, like kscreensaver:

[I] kde-base/kscreensaver
     Available versions:
        (3.5)   3.5.9 (~)3.5.10
        (4.2)   (~)4.2.1 (~)4.2.1[1] [M](~)4.2.2[1]

This one isn't too bad, but recently kdelibs did this and mixing overlay with 
KDE is never a good idea. I can fiddle with PORTDIR_OVERLAY and 
local/layman/make.conf but layman tends to undo my changes.

So how can I mask just a specific ebuild from a specific overlay?

-- 
alan dot mckinnon at gmail dot com