Is this how the tool work?

[linearregression]

So I need a docker-ssh-exec server running by:
docker run -v ~/.ssh/id_rsa:/root/.ssh/id_rsa --name=keyserver -d
mdsol/docker-ssh-exec -server

And what in the Dockerfile in the client?
I need:
ADD pkg/docker-ssh-exec-0.5.2/docker-ssh-exec-0.5.2 /usr/local/bin/docker-ssh-exec-0.5.2
ENV
PATH=$MINT_HOME/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/bin:$PATH
then

RUN docker-ssh-exec-0.5.2 git clone -b master --depth 1 ssh@github.com/lalala/something/something.git /opt

????
It is not clear from the README.
I saw that when the container is building it is broadcasting UDP to keyserver. How it finds the container running the keyserver?