I tried git submodule update --init --recursive
and got following error
error: RPC failed; curl 56 GnuTLS recv error (-54): Error in the pull function.
fatal: The remote end hung up unexpectedly
fatal: early EOF
fatal: index-pack failed
My OS is window 10 and I'm using docker for windows. Docker
images is ubuntu:16.04
Looks like you are missing openssl package, as another option could be network issue.