что такое thin-manifests

Разработка на C# под linux

man portage
/usr/portage/metadata/
layout.conf

thin-manifests = [true|false]
Boolean value whether Manifest files contain only DIST entries.

https://github.com/gentoo/gentoo/blob/master/metadata/layout.conf#L35-L36
# Use thin Manifests for Git
thin-manifests = true

if you set thin-manifests; then the ebuild won't be recorded in the Manifest