Exporter plugin (like frontend but for exporters) #3037
Description
Related #2581
There is a demand for exporting oci-incompatible build artifacts but doing the integration in-tree and the future maintenance looks very challenging.
To move such integration forward, we can support out-of-tree exporter plugins that allows extracting artifacts in arbitrary formats, it'll make the integration and maintenance feasible for advanced artifacts.
It've also been discussed in #2045 (comment)
@tonistiigi
There's a concern of future maintenance cost of this code should it be merged. Would you be interested on taking a look at the problem of providing out-of-tree exporters(or blob converters per #2045 (review)) support instead that would run in containers like buildkit frontends do and what capabilities they would need.
As discussed above, maybe we can have a containerized exporter plugin like done in frontends.