Support for running Spin Applications built inside a container about spin HOT 1 OPEN

First, I am strongly in favor of making it very easy to be able to build Spin apps in containers.
For ease of setup for developer environments, just having Docker configured locally in order to build an application generated from any Spin template would be great — and I would assume would involve adding a Dockerfile to each of our templates.

Would you please expand a bit on:

Currently you can't effectively work around this even by running the compiler in a container as you lose build provenance, but also rely on the host spin implementation to build the OCI artifact while pushing.

What exactly do you mean here by "losing build provenance"?
(trying to understand exactly what we're not able to satisfy while bundling as an artifact that we would as a "real" container image).

While I am strongly in favor of building applications in containers, packaging them in containers is something I have been extremely hesitant of in the past — partly because if you are responsible for manually bundling all the files required for your app, you are now left with keeping each files section for each component in spin.toml in sync with your Dockerfile.
Because of that alone, IMO, spin.toml + scratch container is not the right format to distribute (and building tooling around automating and keeping that in sync basically leads you to designing our current distribution mechanism).

Side note: since Spin apps are made of a several components, each generated from its own template, I imagine you'd end up with several "builder" images, each responsible for building its own template? Or the alternative of a single multi-stage build, with stages for each component.

Side-side note: you also have pre-built components that don't require their own builder, since you fetch them at build time from some source (today HTTPS endpoints).

from spin.