Description of problem:
The project-clone init container cannot process a git clone from Gitlab by SSH over a proxy. The proxy command in ssh_config doesn't work with ssh, only with nc, but nc is not part of the container:

Working:

ssh -o "ProxyCommand nc -X CONNECT -x 10.20.30.40:8080 %h %p" -o Port=12322 code.example.com

Not Working:

ssh -i /etc/ssh/dwo_ssh_key -o 'ProxyCommand ssh 10.20.30.40 -W %h:%p' -T git@code.example.com -p 12322

This means that the customer is not able to clone the repository from the code.example.com 

HTTPS is not an option because the personal access tokens for GitLab are only valid for 24 hours. The connection with the git clone was successfully tested by SSH with nc as ProxyCommand. So, the easiest solution would be to extend the image with the netcat (nc) tool.