Refactor multi-arch apt setup

[0xh3rman]

Summary

• move multi-arch apt setup into a dedicated script
• keep Dockerfile readable with a single RUN line

Testing

• not run (Docker build verified earlier)

[gemini-code-assist]

Summary of Changes

Hello @0xh3rman, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on improving the Docker image build process by refactoring the multi-architecture APT setup. The changes aim to make the Dockerfile cleaner and more modular, while also enhancing the robustness of tool installations across different CPU architectures. This leads to a more maintainable and adaptable build environment.

Highlights

• Dockerfile Refactoring: The multi-architecture APT setup logic has been extracted from the main Dockerfile into a dedicated shell script, significantly improving the Dockerfile's readability and maintainability by reducing the complexity of the RUN commands.
• Dynamic just Tool Installation: The installation of the just tool now dynamically determines the correct target architecture (x86_64-unknown-linux-musl or aarch64-unknown-linux-musl) based on the TARGETARCH build argument, enhancing cross-platform compatibility.
• New Multi-Arch Setup Script: A new script, scripts/setup-multiarch-apt.sh, has been introduced to encapsulate the logic for adding amd64 architecture support and installing necessary amd64 libraries (like libc6 and zlib1g) specifically for arm64 hosts, to support x86_64-only binaries like aapt2 under emulation.
• Base Image Tag Update: The base image tag in reproducible/base_image_tag.txt has been updated to base-2026-01-30.

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Changelog

• Dockerfile
  • Removed the JUST_TARGET ARG definition from the initial block.
  • Added TARGETARCH as a build argument.
  • Replaced the inline multi-architecture APT setup RUN command with a COPY instruction for the new setup-multiarch-apt.sh script and a subsequent RUN command to execute it.
  • Modified the just tool installation RUN command to use a case statement to set JUST_TARGET based on the TARGETARCH build argument.
• reproducible/base_image_tag.txt
  • Updated the base image tag from base-2025-12-18 to base-2026-01-30.
• scripts/setup-multiarch-apt.sh
  • Added a new executable shell script responsible for configuring multi-architecture support for APT.
  • The script conditionally adds amd64 architecture and configures ubuntu-amd64.sources if the current architecture is arm64.
  • It installs essential libraries (libc6, libstdc++6, zlib1g, libtinfo6, ca-certificates) for the native architecture, and additionally libc6:amd64 and zlib1g:amd64 if running on arm64.

Ignored Files

• Ignored by pattern: .github/workflows/** (2)
  • .github/workflows/publish-base-image.yml
  • .github/workflows/verify-apk.yml

Activity

• No specific activity recorded for this pull request.

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[gemini-code-assist]

Code Review

This pull request refactors the multi-architecture apt setup into a dedicated script, which improves the readability of the Dockerfile. It also correctly handles multi-arch builds for installing just. The changes are a good improvement, but I've found a couple of potential issues in the new script: a risky default value for the Ubuntu codename and missing packages for amd64 emulation on arm64 hosts compared to the previous implementation. Addressing these will make the setup more robust.