"Sample pkg_postinst" and "Common pkg_postinst Tasks" suggest using has_version in pkg_postinst in order to detect upgraded. This does not work anymore with >=portage-2.1.5 since it runs pkg_postinst after the old version have been removed.
This doesn't seem that hard to fix, and is a blocker for portage-2.1.6.1. Do somebody need any help with this?
Juan, A patch will make this happen a lot quicker. http://devmanual.gentoo.org/appendices/contributing/
Sending trunk/ebuild-writing/functions/pkg_postinst/text.xml Transmitting file data . Committed revision 136. Let me know if I misrepresented anything in the new version.