cross-reference meta for a lightweight way to automatically notify image maintainers on base image deprecations ("naughty from")

[tianon]

When an image/tag is removed, we can cross-reference docker-library/meta's sources.json for a really cheap way to get a list of "affected" images so we can automatically ping their maintainers and inform them (instead of the very manual comments we currently try to remember to make because before now the calculation was an expensive one).

jq '.[] | select(del(.arches[].parents.scratch) | any(.arches[].parents[]; .sourceId == null and .pin == null)) | first(.arches[].tags[])' sources.json

.[]
| select(
	del(.arches[].parents.scratch)
	| any(.arches[].parents[]; .sourceId == null and .pin == null)
)
| first(.arches[].tags[])