I have java in my USE. Because of this 'emerge --world update' installed dev-java/blackdown-jdk and dev-java/java-config. So far so good. But another 'emerge --pretend --world update' wants to install dev-java/blackdown-jre although the jdk provides a jre. If i remove the line 'virtual/jre dev-java/blackdown-jre' or replace in this line the blackdown-jre with blackdown-jdk in the files /usr/portage/profiles/default-1.0_rc6/virtuals or /etc/make.profile/virtuals emerge is satisfied and don't want to install the jre anymore.
I forget to mention that the fix to modify one of the two files is only temporarie because it doesn't survives an 'emerge rsync'.
Whoops... wrong bug. Issue is still open.
OK, the current world functionality has been removed from cvs emerge and is pending reimplementation.