Fall back to build from Dockerfile when image not downloadable

[MartinLoeper]

Is it possible with the current spec to configure that the devcontainer should be built from given Dockerfile if the specified image cannot be pulled?

As far as I understand, the "build" and "image" properties are mutually exclusive, i.e. the devcontainer is either "Image based" or "Dockerfile based" to say it in the words of the spec.

My usecase is to provide an escape hatch for unreliable internal docker registries. I want developers to be able to build their local devcontainers on their own machines in case the company's docker registry is unreachable for some reason.