Proposal: Support abstract image tags for different release versions/lines/flavors

[lufzle]

Right now tags are very specific, e.g. node:8.4.0-29. This doesn't allow us to use a wildcard version in our images, instead we can either fetch the latest tag or a very specific one:

# Fetch latest image to be pushed (could be 6 or 8, whatever was pushed last)
FROM registry.opensource.zalan.do/stups/node

# Fetch very specific version
FROM registry.opensource.zalan.do/stups/node:8.4.0-29

My proposal is to rename the tags to node-{version}[-{flavor}], examples:

# Fetch latest Node 8
FROM registry.opensource.zalan.do/stups/node-8

# Fetch specific Node 8 version
FROM registry.opensource.zalan.do/stups/node-8:8.4.0-29

# Fetch latest for LTS in Alpine flavor
FROM registry.opensource.zalan.do/stups/node-lts-alpine:latest

# Fetch latest for Node 6 in Alpine flavor
FROM registry.opensource.zalan.do/stups/node-6-alpine

# Fetch latest for Node Current
FROM registry.opensource.zalan.do/stups/node-current

[lufzle]

@dryewo sometime ago you mentioned this in the chat; I was in disagreement at that time but now I understand your point and actually agree that this is probably a better approach. Could you please check it out and share your thoughts?

[dryewo]

As far as I remember, I proposed to make Node major version a part of the image name, not its tag.
That would allow us have latest tag per Major version "for free". That is pretty much in line with what you are proposing now.