Description

We would like to be able to add metadata to our buildpacks via image labels at build time but there is no way for us to add custom image labels.

Proposed solution

Add a flag --label <label>=<value> to pack buildpack package command that will allow buildpack authors to add custom metadata to the buildpack image at build time.

Describe alternatives you've considered

This can be achieved with crane mutate but that requires you to upload the image without metadata to a registry and then mutate the file. This also means that image labels cannot be added to the .cnb files at all which feels bad as the OCI image in registry and in .cnb file format should be identical.