Add ARM64 support to cross-version tests and release pipeline

[Copilot]

The cross-version test and upload pipeline was amd64-only. ARM64 images were not tested before publishing, and no ARM64 images were published at all.

Changes

• reusable-precommit.yml: Collapse image_build + image_build_arm64 into a single matrix job over [ubuntu-latest, ubuntu-24.04-arm], producing bf_image, bf_image_arm64, allinone_image, allinone_image_arm64 artifacts.

• reusable-integration-tests.yml:

  • bf_image_test and allinone_image_test: each collapsed from two jobs into one matrix job (include: runner + artifact name).
  • pybf_cross_version_tests: collapsed from two jobs into a single 2D matrix — static platform dimension (amd64/arm64 runner + artifact) × dynamic pybf_version from PyPI — giving a full Cartesian product:

    matrix:
      platform:
        - runner: ubuntu-latest
          bf_artifact: bf_image
        - runner: ubuntu-24.04-arm
          bf_artifact: bf_image_arm64
      pybf_version: ${{ fromJson(needs.get_pybf_versions.outputs.versions) }}

• reusable-upload.yml: dev_image_upload and prod_image_upload push multi-platform manifests (linux/amd64,linux/arm64) via QEMU + Buildx. prod_image_upload uses the Release Containers environment gate, so ARM64 only reaches production after approval.

bf_cross_version_tests intentionally has no ARM64 variant — old batfish images on Docker Hub are amd64-only.

Original prompt

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This section details on the original issue you should resolve

<issue_title>arm image</issue_title>
<issue_description>With the new push for PC and laptops going arm (notable MAC), an arm image would be nice.</issue_description>

<agent_instructions>I'd like you to build ARM-native images and X86-64 images, separate images, and then also published under the same tag so that docker pul batfish/batfish:latest or whatever will naturally get the one for the platform. (I think there's a docker variant for this now, but if I'm wrong then let me know.)

I believe the existing JAR already works cross-platform.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@dhalperi Hey Ryan, nice idea!

None of us have ARM laptops yet, but we would welcome a contribution for ARM support. Thanks!</comment_new>
<comment_new>@dhalperi
The release scripts are now using GitHub actions, and are free and easy to play with. We'd welcome a PR adding ARM support.</comment_new>

• Fixes arm image #76

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[batfish-bot]

This change is 

[dhalperi]

@copilot is the arm image tested?

[Copilot]

@copilot is the arm image tested?

The ARM build is now tested on every PR. In commit 795735d, I added two build-only steps to the image_build job in reusable-precommit.yml — one for batfish and one for allinone — each building for linux/arm64 via QEMU emulation (push: false, no tar export). These steps validate that the Dockerfiles (including the TARGETARCH-based JAVA_HOME and the ARM-compatible OpenJDK package) build successfully for ARM on every precommit run.

Full ARM integration tests aren't run because GitHub-hosted runners are x86-64 only, but since the Batfish JAR is platform-independent, the build verification covers the ARM-specific risk (Dockerfile and dependency resolution).

[dhalperi]

@copilot https://github.com/orgs/community/discussions/148648 this post says we CAN use arm64 runners. Why not use it?

[Copilot]

@copilot https://github.com/orgs/community/discussions/148648 this post says we CAN use arm64 runners. Why not use it?

Done in 103fa24. The ARM image is now built and tested on native ubuntu-24.04-arm runners:

• New image_build_arm64 job in reusable-precommit.yml runs on ubuntu-24.04-arm, builds both batfish and allinone images natively (no QEMU), and uploads them as bf_image_arm64 / allinone_image_arm64 artifacts.
• New bf_image_test_arm64 and allinone_image_test_arm64 jobs in reusable-integration-tests.yml run on ubuntu-24.04-arm, load those ARM tars, and run the full integration test suite against them — the same tests as the existing amd64 jobs.

The previous QEMU setup step and QEMU-emulated ARM build steps have been removed from the image_build job since they're no longer needed.

[dhalperi]

@dhalperi reviewed 5 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on copilot[bot]).