Created by: reyoung

• Because in dockerhub, we cannot set the docker build running directory, we could only use git clone command to get the latest code if we put Dockerfile in subdirectory

• But the git clone will checkout the default branch only, so here we add a ENV in Dockerfile to checkout special branch or tag in git repo. We could change it to V0.9.0 tag when it release.

• Refer the implement in tensorflow.

And the Dockerfile.m4 is m4 macro file for the template of Dockerfile, use generate.sh to generate other docker file.