Dind tagged docker versions

[lox]

This adds specific versions of the dind agent with specific versions of Docker, as otherwise it's just the latest upstream image: https://github.com/jpetazzo/dind/blob/master/Dockerfile#L13

This will correspond to tags:

• dind - whatever the latest is
• dind-X.X - whatever the most recent minor release of X.X is
• dind-X.X.X - a specific version

[lox]

@toolmantim Thoughts?

[lox]

Test builds here if anyone wants to try them https://registry.hub.docker.com/u/lox24/buildkite-agent/

[lox]

This is what my automated build setup on docker hub looks like:

http://lachlan.me/s/5fdrp.png

[toolmantim]

Ah yeah, I definitely see how this is needed. I was wondering how to best to set this up when you want parity with the host docker. :+1: Will set this up and merge it in.

[toolmantim]

Also perhaps the DIND images themselves should have this? Is there any reason we couldn't send a PR to them, and then just depend on FROM jpetazzo/dind-1.7 etc?

[lox]

Yup, that sounds really sensible @toolmantim. Will do that.

[toolmantim]

I just realised though, we can easily update this when the upstream images have been updated too. In the mean time we can easily just ship these… it's not like the tags will change?

[toolmantim]

I've merged these and have updated docker hub automated builds config. They're building now :+1: Thanks Lach!