image content specific tag

[cppforlife]

Describe the problem/challenge you have

as part of integrating kubectl buildkit into carvel-dev/kbld#63, i ended up generating random tag everytime kbld command runs. tag needs to change when image changes so that resources in k8s observe that there was an image change (keeping same tag would not trigger a change in k8s even if tag is pointing at a new image).

i would like to have a tag that changes when image changes, and does not change when image stays the same. image digests are used exactly used for this, however (to my surprise some time ago), Docker daemon does not allow to reference local images by digest (only by tag). e.g. in k8s, doing image: foo@sha256:... does not work when foo is a local image.

Description of the solution you'd like

allow special identifier within a tag that would get replaced by digest. e.g. foo:custom-${digest}-something would be resolved to foo:custom-sha256-0f8393dca...-something. this provides uniqueness of a tag and stability. (as a note, kbld only uses tags when interacting with Docker daemon, as soon as image is pushed to registry only digest reference is used).

Vote on this request

This is an invitation to the community to vote on issues. Use the "smiley face" up to the right of this comment to vote.

• 👍 "This project will be more useful if this feature were added"
• 👎 "This feature will not enhance the project in a meaningful way"