I use a central machine that all other gentoo machines pull portage updates from using emerge set up for git.
Some 10+ physical and virtual machines work fine. A newly installed machine wants a git password to do the git pull where as no other machine does. Tried setting up keys for it on the remote machine (user portage which is who git pulls come from) and ssh login works fine, git demands a password. Any hints because its got me beat! BillK