A tool called remerge would be quite useful. syntax: remerge [options] packs remerge would emerge the target packages, using exactly the same version of the already installed ones (even if masked or outdated). The main option (but others may come) would be: -F ["<flags list>"] remerge only packets whose USE flags in the installed version differ from the ones specified in environment variables. If flags list is provided, process only the the specified flags. This would be very handy to add a USE flag to already installed packages. At the moment, this can't be done without doing it manually or doint a _really_ big mess with "emerge -e world" and sed; the latter solution doesn't even work if you have any masked packages that need to be remerged with the new flag. example: remerge -F "ipv6 dvd alsa" world all installed packages in which the USE flags for ipv6, dvd or alsa differ between the installed version and make.conf will be remerged, no matter if outdated or masked, using exactly the same version.
*** This bug has been marked as a duplicate of 5075 ***
