400 Bad request when building images with registry cache to ECR

[angonz]

Bug description
When building images with registry cache, and when the cache is in AWS' ECR, building results in 400 Bad request error.

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 > importing cache manifest from 2xxxxxxx4.dkr.ecr.us-east-1.amazonaws.com/myrepo/openedx:202409032122-cache:
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 > exporting cache to registry:
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error: failed to solve: rpc error: code = Unknown desc = error writing manifest blob: failed commit on ref "sha256:dbddfa9dc32dd219457de9c9b1534f667024da6e36e5a085f7f52540fc9ef9af": unexpected status from PUT request to https://2xxxxxxx4.dkr.ecr.us-east-1.amazonaws.com/v2/myrepo/openedx/manifests/202409032122-cache: 400 Bad Request
Error: Command failed with status 1: docker buildx build --tag=2xxxxxxx4.dkr.ecr.us-east-1.amazonaws.com/myrepo/openedx:202409032122 --output=type=docker --builder=container --cache-from=type=registry,ref=2xxxxxxx4.dkr.ecr.us-east-1.amazonaws.com/myrepo/openedx:202409032122-cache --cache-to=type=registry,mode=max,ref=2xxxxxxx4.dkr.ecr.us-east-1.amazonaws.com/myrepo/openedx:202409032122-cache /home/myuser/mytutorroot/env/build/openedx
Error building openedx

How to reproduce

• Create an ECR registry in AWS
• Declare the registry url in the DOCKER_REGISTRY variable
• Log in to ECR
• Run tutor images build openedx --cache-to-registry

Environment

Tested with Tutor 17.0.6

Additional context

As per this document, adding image-manifest=true context to the docker buildx command fixed the issue.

The new context key introduced in Buildkit 0.12 here is image-manifest. Setting this key’s value to true lets you now store an OCI-compatible version of a remote cache in the registry.

If it doesn't break the official repos (which I cannot test), I would like to add this key to the image build args.

[angonz]

I have just hardcoded the image-manifest=true to the build command in PR #1119. Please check if it doesn't impact negatively in the official, public Docker registry.
Another option would be to do it under another option, like --cache-to-registry-oci or similar.