Disclaimer: this bug has been filed in a semi-automated manner.
When emerging the package sys-kernel/genkernel-3.4.24_p2, the following elog messages are displayed:
* The LUKS support has changed from versions prior to 3.4.4. Now,
* you use crypt_root=/dev/blah instead of real_root=luks:/dev/blah.
Such messages should only be displayed when the package is upgraded from an old enough package (and possibly for new installs).
These situations can be checked in the ebuild as follows:
if has_version '<sys-kernel/genkernel-1.0'; then
Or, if the message should also be displayed for new installs:
if !has_version 'sys-kernel/genkernel' || has_version '<sys-kernel/genkernel-1.0'; then
Remember to replace 1.0 with the right version number.
See the tracker bug 440214 for more details.
What if they didn't read it before? It stays.