Modernise usage of Docker Hub (link to Dockerfile & automated builds from alpine base image)

[MPV]

Hi,
Would you be open to modernise the usage of Docker hub for this image/repo?

1. No Dockerfile shown:

Today you can't see any Dockerfile here https://hub.docker.com/r/alpine/git/

This, in combination with that it's not easy to find this GitHub repo from the above page, makes this image seem not-so-trustworthy.

2. No automated builds

If the base image alpine is updated, this image isn't rebuilt and kept up-to-date.

Would you be open to adding this?

[ozbillwang]

1. No Dockerfile shown:

updated the readme in hub.docker.com with github repo url and travis ci build url.

2. No automated builds

set cronjob in travis.ci to run automation build every month, it will generate two tags:

• incremental release / tag version
• git version - alpine/git:v${GIT_VERSION}