FR: Support partial installation

[thesayyn]

Currently, apt rules assume that installations always happen from scratch, meaning that the underlying system does not have any apt packages installed on it.

This is true if you are building a base image with rules_distroless, but often users use a base image that has some apt packages already installed, making rules_distroless suboptimal at best.

I am proposing a feature where the manifest can instruct our resolver to continue where base image left off reusing package information at /var/lib/dpkg/status within the base image or expect users to list all the packages that already present.

Option 1

In terms of DX, this api is unpleasant, but comes with great flexibility.

manifest.yaml

exclude:
    - base-files
    - base-passwd
    - bash

Option 2

This option autimatically derives the package information by walking through layers. While easier to use since users already have a base image passed to oci_image and can easily add it to their apt.install calls, is less flexible.

apt.install(
 
   base = "@base_image_from_oci_pull"
)

[jeanmorais]

It would be great having this feature.

[thesayyn]

I would like to work on this but my time is really limited these days. I'd review A clean PR with tests added however.