Tag vs Image Name vs Image Reference

[jromero]

Based on this PR: buildpacks/pack#1266 (review)

To be honest, I'm a slightly, slightly conflicted by this. Although the help message is correct, it implies that pack is treating a "tag" differently than other tools in the ecosystem. And it's not.

I think this confusion already exists within the ecosystem. (Thanks docker :P). There is no clear separation between tags and image names.

• Tags "optionally" include tags.
  • "must tag it with the registry hostname and port"
• With the creation of the distribution spec, the "tag" misuse may actually be cleared up.
  • "A container engine would like to run verified image named "library/ubuntu", with the tag "latest"."
• FWIW, tag in crane does actually mean anything following : in the image reference

Maybe it's worth proposing that we move the needle on clarifying the distinction ourselves as well. image reference vs tag.

Format

pack build <img-ref> --tag <tag>
  - <img-ref> = image reference in format "<img-name>[:tag]"  
  - <img-name> = image name (excluding tag) in format "[host/]<repo>"
  - <tag> = tag as defined in OCI distribution spec

NOTE: host defaults to index.docker.io but that's a separate issue. 😓

Example 1

pack build myapp --tag v1

This would create two tags for the following image "index.docker.io/myapp":

• latest (may be referenced via index.docker.io/myapp:latest)
• v1 (may be referenced via index.docker.io/myapp:v1)

Example 2

pack build myapp:v1 --tag v1.2

This would create two tags for the following image "index.docker.io/myapp":

• v1 (may be referenced via index.docker.io/myapp:v1)
• v1.2 (may be referenced via index.docker.io/myapp:v1.2)

We'd proba

We'd probably want lifecycle buy-in as well. cc: @ekcasey / @natalieparellano