Makefile+tools: reduce LND linter docker image size by 85% from 2330 MB to 355 MB

[mohamedawnallah]

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[gemini-code-assist]

Summary of Changes

Hello @mohamedawnallah, 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 aims to drastically reduce the size of the LND linter Docker image. This is achieved by migrating to an Alpine-based Go image and optimizing the build process within the Dockerfile, complemented by corresponding adjustments in the Makefile for cache handling. The primary impact is a more efficient CI/CD pipeline due to smaller image downloads and reduced storage requirements.

Highlights

• Significant Image Size Reduction: Reduced the LND linter Docker image size by 85%, from 2330 MB to 355 MB, leading to faster downloads and reduced storage.
• Base Image Migration: Switched the tools/Dockerfile base image from the larger golang:1.24.6 to the more lightweight golang:1.24.6-alpine.
• Build Process Optimization: Implemented apk for package installation and added post-build cleanup steps in the Dockerfile to remove build caches and temporary files, further minimizing the final image size.
• Makefile Cache Alignment: Updated the Makefile to align Docker volume mounts for Go build caches with the new Dockerfile structure, and removed the explicit GOMODCACHE mount.

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[gemini-code-assist]

Code Review

This pull request significantly reduces the LND linter docker image size by switching to an Alpine base image and implementing multi-stage build-like optimizations within a single RUN command to clean up build dependencies and caches. The changes are well-executed and effective. I have one minor suggestion for the tools/Dockerfile to further optimize the image size by handling the apk cache more efficiently. The related changes in the Makefile are correct and align with the new Docker image structure.

[gemini-code-assist]

While this change correctly switches to apk for the Alpine base image, there's a small improvement to further reduce the image size. The apk update command creates a cache in /var/cache/apk/. In your later RUN command on line 17, you remove this cache with rm -rf /var/cache/apk/*.

However, because the removal happens in a different RUN instruction (and thus a different Docker layer), the cache files from this layer will still be part of the image, even though they are marked as deleted in a later layer.

To avoid this and make the image even smaller, you should perform the cleanup in the same RUN instruction. After applying the suggestion below, you can remove the rm -rf /var/cache/apk/* from the RUN command on lines 11-18.

RUN apk update && apk add --no-cache git && rm -rf /var/cache/apk/*