Each gentoo developer may make new ebuilds for both main gentoo tree and for each overlay.
So, he should have several github projects - one for the fork of gentoo tree, one for forks of each overlay.
Layman should know which overlays belong to this developer.
Configuring layman for personal overlays will allow to test ebuilds when they are not yet accepted to the corresponding upstreams
So somewhere should be the file on github with the metainformation about overlays (list of personal overlays)
Also developer probably will write notes about his steps. I think it is possible to combine personal site with the list of personal overlays.
"overlays:" section of /etc/layman/layman.cfg
Add some line similar to this one:
https://raw.githubusercontent.com/ArsenShnurkov/shnurise/master/github-gentoo-dotnet-metadata-for-layman.xml
To change repository name locally without modification of .gitignore file:
git update-index --assume-unchanged profiles/repo_name
This labels the file "profiles/repo_name" as unchanged, even if it differs from the content of online repossitory