Emerge supports the ROOT environment variable. ROOT enables emerge to target a separate Gentoo file system for updates, etc. When one uses emerge with ROOT set to something other than "/" and emerge places new config files in ${ROOT}/etc/init.d, the dispatch-conf script is unable to process the new config files. The dispatch-conf script handles files only in /etc/init.d -- not ${ROOT}/etc/init.d. The etc-update script properly pays attention to the ROOT environment variable, and processes new config files in ${ROOT}/etc/init.d. The dispatch-conf script should pay attention to the ROOT environmental variable just as the etc-update script does.
ran into this today and am wondering is this on anyone's radar that's capable of doing this enhancement? or some qualified assessment on how low this fruit is hanging?
In portage-2.1.10.41 and later there's a PORTAGE_OVERRIDE_EPREFIX variable that will give dispatch-conf the behavior that you want. However, this variable is experimental and support for it is subject to change.
https://github.com/gentoo/portage/commit/0505c2e37bdfe3279bc4d1effcc4c1bb5148aa9e