Note: while the use-case described is about using submodules within a project, the same applies to a normal git clone
of a repository over HTTP.
I have
For me the git:// just doesn't work through the proxy although the https:// does. This caused some bit of headache because I was running scripts that all used git:// so I couldn't just easily change them all. However I found this GEM
git config --global url."https://github.com/".insteadOf git://github.com/