Users should be able to set desired git branch, by default live ebuilds should build master branch, unless there are strong reasons to choose other. For x264 there are no such reasons: master branch never fails to build or work and contains latest stuff. Now there is nonsense situation for x264 ebuilds: live ebuilds install older code, then latest non live.
it could be done by two different live ebuilds 0.9999 vs 9999 or 9999 vs 9999999 for example