On publishing Tekton OCI Bundle from the catalog

[vdemeester]

Today, we publish on bundle per resource (Task) and use tag as version. I think it works
fine but kind of defeat the purpose of the bundle being able to package multiple
resources.

Given the versions of each resources in the catalog, one catalog cannot be re-presented as
one oci bundle :

• when does a new catalog image is published ? each time a new task is updated/added/… ?
• How the version increase ?
• What task version is shipped in what catalog image ?

The upstream catalog could continue ship one bundle per resource as it does today, but
also add some way to define "bundle" that package a set of task (version). For example:

• go bundle
  • =go:1.0= ships go-build:0.2, go-test:0.3, golangci-lint:0.2, …
  • =go:2.0= ships go-build:0.4, go-test:0.4, golangci-lint:0.5, …
• s2i bundle ships buildah and s2i task

This could be defined in a =bundles= folder in the =catalog= repository and kept up-to-date
(and bumped) by the maintainers. Then a set of plumbing job would ensure those are
published, …

This raise some concerns or questions around the design of the Tekton OCI Bundle and how we reference them.
We may also want to look into OLM is handle this with bundle — a versioned operator — and index images (also called catalog) — a versionned list of operators.

[vdemeester]

/cc @tektoncd/catalog-maintainers