Hi,
I have been some time without reporting my work at this mailing list and i will send my report for the last weeks.
When i sent my last e-mail I was working on emerging a package from one specific repository using emerge package::repository syntax. It is now working. It's possible to use the ::repository syntax in emerge command line, ebuild dependencies and when masking/unmasking/setting use flags in /etc/portage/package.*. 
I also implemented support for syncing portage tree for several version control systems (git, svn, darcs, hg, bzr, ) and changed emerge --sync to sync all repositories in repos.conf with SYNC variable set. Its possible to sync just one repository using emerge --sync repo_name. It's possible to select which vcs will be used in SYNC variable, using the protocol in uri. If you want to download from a git repo using http you can use: SYNC=git+http://servername/repo.git.
After that i wrote a test in pym/portage/tests to use some provided ebuilds to check if emerge is selecting the correct repository when using ::repository syntax. I am working now in improving this tests and writing tests for package.* files and syncing. 

That's all,
Otávio Pontes