I suggest to add a test, for "HOMEPAGE.missinghttp": "Ebuilds that have a missing http(s):// in the HOMEPAGE variable", see https://devmanual.gentoo.org/quickstart/index.html
we don't want to mandate any protocol. ftp:// is perfectly valid for example. probably also want to permit file paths for local/site ebuilds.
Patch posted for review: https://archives.gentoo.org/gentoo-portage-dev/message/3110ee4f406c0bf96740626a07cb5ac6 https://github.com/gentoo/portage/pull/88
This is in the master branch: https://gitweb.gentoo.org/proj/portage.git/commit/?id=55dedaa865334543e51693838700dcf5e72754d2
Released in repoman-2.3.2