WIP: commit: optionally create layers for ADD/COPY/RUN/WORKDIR

[nalind]

trafficstars

What type of PR is this?

/kind bug

What this PR does / why we need it:

In multi-layer mode, only add layers when ADD, COPY, RUN, or WORKDIR make changes to the container's rootfs.

How to verify it

Building an image using --layers=true and a Dockerfile containing

FROM fedora
WORKDIR /testdir

should produce an image with two layers, rather than just the base image's single layer.

Conformance tests have been extended to compare how many layers we generate in comparison to docker build, though it makes exceptions for items we create as targets for bind mounts when handling RUN instructions.

Which issue(s) this PR fixes:

Fixes #2402

Special notes for your reviewer:

The workdir-in-image-owner and workdir-not-in-image conformance tests should exercise this.

Does this PR introduce a user-facing change?

Instead of always creating new layers for ADD, COPY, and RUN instructions, `buildah build-using-dockerfile --layers` will now avoid adding new layers when those instructions make no changes to the filesystem.

[rhatdan]

What happens if I have

FROM fedora
WORKDIR /home/dwalsh
MAINTAINER dan walsh

[nalind]

That doesn't work right. Moving this to a draft PR.

[openshift-ci-robot]

@nalind: PR needs rebase.

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[openshift-ci-robot]

@nalind: PR needs rebase.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[rhatdan]

@nalind Any movement on this one? Needs a rebase.

[rhatdan]

@nalind Maybe we should just get this merged since it closes one of the cases. Then we can continue to work on the corner cases.

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nalind

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[nalind]

/retitle commit: optionally create layers for ADD/COPY/RUN/WORKDIR

[nalind]

I expect conformance tests to fail on overlay because resetting the contents of a directory causes us to mark it as opaque until #2756 changes how we do things for those cases.

[github-actions[bot]]

A friendly reminder that this PR had no activity for 30 days.

[rhatdan]

@nalind Is this still being worked on or can we close it?

[nalind]

We still need this.

[rhatdan]

@nalind can you rebase and repush?

[github-actions[bot]]

A friendly reminder that this PR had no activity for 30 days.

[rhatdan]

@nalind rebase and repush.

[openshift-ci[bot]]

@nalind: PR needs rebase.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[rhatdan]

@nalind this oldy-but-goody PR needs a rebase.

[github-actions[bot]]

A friendly reminder that this PR had no activity for 30 days.

[rhatdan]

@nalind what is going on with this PR?

[nalind]

A simple rebase isn't going to be enough here - it didn't pass all of the tests before it needed that. Re-adding the WIP label.

[github-actions[bot]]

A friendly reminder that this PR had no activity for 30 days.