eapply_user in portage does: for d in "${basedir}"/${CATEGORY}/{${P}-${PR},${P},${PN}}{,:${SLOT%/*}}; do epatch_user does: for check in ${CATEGORY}/{${P}-${PR},${P},${PN}}{,:${SLOT}}; do I think portage using ${SLOT%/*} is more correct
commit 5a08a63420601a47075da957e25dbc909ce33aef Author: Alexis Ballier <aballier@gentoo.org> Date: Wed Feb 17 22:07:59 2016 +0100 eclass/eutils.eclass: epatch_user: Strip subslot when taking patches from /etc/portage/patches/$CAT/$PN:$SLOT. Bug #574966. This makes it similar to what portage does with eapply_user. it was so trivial, and epatch_user being more or less deprecated, that i took the liberty to change it (i dont think $SLOT containing slashes can even work)
seems fine: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=5a08a63420601a47075da957e25dbc909ce33aef as long as the SLOT only has one / that'll work fine. thanks!