Disclaimer: this bug has been filed in a semi-automated manner.
When emerging the package app-misc/screen-4.0.3-r5, the following elog messages are displayed:
* Some dangerous key bindings have been removed or changed to more safe values.
* We enable some xterm hacks in our default screenrc, which might break some
* applications. Please check /etc/screenrc for information on these changes.
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 '<app-misc/screen-1.0'; then
Or, if the message should also be displayed for new installs:
if !has_version 'app-misc/screen' || has_version '<app-misc/screen-1.0'; then
Remember to replace 1.0 with the right version number.
See the tracker bug 440214 for more details.
I'm using REPLACING_VERSIONS from EAPI-4 for checking new installs.