I heard that gentoo has portage delta snapshots, I haven't tried them yet, also I know now that there is a tool to use them 'app-portage/emerge-delta-webrsync', briefly looking at the source of that script it looks like it supports FEATURES="webrsync-gpg"? I'm filing this request if it's possible to auto-sign delta snapshots too. I guess that can reduce the traffic to mirrors, also help people with slow connections (like me) or people with limited amount of data per period downloading portage tree updates. Reproducible: Always