I tried updating the gst-plugins-vaapi git ebuild to git-r3, as it relies on submodules which are quite broken in git-2. When it tries to checkout the first submodule, it fails to create the branch. Reproducible: Always
Created attachment 359588 [details] gst-plugins-vaapi-9999.ebuild
Created attachment 359590 [details] build.log
Thanks for the report. I will try to reproduce this in a few minutes and then try to find out what's wrong :).
Ok, this happens because the commit is not on 'master', and fetch seems to focus on that branch only. I will need to think how to solve this, to be honest...
I've just committed a fix. It should appear on the mirrors after a few hours, and the everything should start to work.