Rename to java8_maven_git

[dsmiley]

I don't think "docker" should be in the published name of this image on Docker Hub. It's not like this image has Docker CLI stuff or other meta-docker stuff. It's just a docker image with Java 8, Maven, and Git.

BTW there are already "maven" images, and of course such images include Java be necessity... so perhaps instead you should inherit from one of those and then add git?
https://hub.docker.com/_/maven/ e.g. 3-jdk-8-alpine