This is my personal overlay of Gentoo GNU/Linux ebuilds.
If you want to add them for whatever reason use app-eselect/eselect-repository
From gentoo-mirror (recommended - has metadata cache pregenerated):
# eselect repository enable xarblu-overlay
From here:
# eselect repository add xarblu-overlay git https://github.com/xarblu/xarblu-overlay.git