Diffs in Docker builds don't show up as diffs

[joeduffy]

Due to the way we perform Docker builds, the Image resource never shows any diffs. This is confusing because, even if there are "no changes" shown, performing a pulumi up actually runs the command to perform the side effects of building and pushing the image.

Instead, I believe we should do the build and either use the resulting digest hash as an input property for the resource -- such that if the hash changes, it appears as a diff to the resource -- or, if that's not appealing, we should treat changes to output properties as a diff in the output.

[lukehoban]

I believe this is (another) reason why we need to do #132 (just opened to track more explicitly).

[dbeattie71]

I was just looking at how this works and I'm not sure docker inspect will work for coming up with a hash of an image on two different machines without getting a different result. Does that sound right? It would be nice to override the funtionality in BuildImageAsync that gets the inspectResult so a custom implementation can be created.

[leezen]

Cross-posting for posterity, but one option is to use the RegistryImage resource (see #132 (comment) for more details on using it as a replacement for Image)

[AaronFriel]

This issue is resolved with the new implementation of the Docker Image resource in v4! See our blog post for more info: https://www.pulumi.com/blog/build-images-50x-faster-docker-v4/