Some projects under git vcs, using submodules, intentionally prefer unsafe git protocal instead of https for submodules, without all chances for fix ruined. I just got first serious reason, like of OSX 10.5 compatibility, though can't find words to google more about it: https://github.com/x42/x42-plugins/pull/2 It could be posible to do substitution in src_unpack() if there were separate functions to fetch without submodules, than fetch single level, which would be used after substitution in each of them, but it seems to be enough complex to deserve place in eclass. So, I see at least 1 usage - substitude git/http with https for certain hosts, that are known to support it automatically. Github, gitlab, savannah, sourceforge are certain - these could be configured by default.
Sounds like bug #661094
