.dockerignore: allowlist for copying into the Docker context

[schildbach]

Without this change, any files in the project directory will be copied into the Docker context when using "docker build". Note this includes git-ignored and dirty files like passwords, wallets, possibly git history, and so on.

This uses quite a lot of disk space, causes unnecessary I/O and renders the Docker cache invalid even on the slightest change to the project.

The current Dockerfile doesn't use the context at all, and dev.Dockerfile only needs a fraction of it. So we ignore everything that isn't explicitly allowed.

[gemini-code-assist]

Summary of Changes

Hello @schildbach, 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 introduces a .dockerignore file to optimize Docker build processes. By ignoring all files by default, it prevents the copying of extraneous data, which previously led to increased disk space usage, I/O operations, and frequent cache invalidations. This change enhances build efficiency and security by ensuring only necessary files are considered during the Docker build, as the Dockerfile currently fetches dependencies directly from GitHub.

Highlights

• Optimized Docker Build Context: Introduced a .dockerignore file to prevent unnecessary files from being copied into the Docker build context, significantly reducing build times and disk usage.
• Enhanced Security: Prevented sensitive files like passwords and wallets from being inadvertently included in the Docker context, improving security posture.
• Improved Cache Invalidation: Addressed issues with Docker cache invalidation caused by minor project changes, leading to more efficient builds.

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Changelog

• .dockerignore
  • Added a new .dockerignore file to exclude all project files from the Docker build context.

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[gemini-code-assist]

Code Review

This pull request aims to improve Docker build performance and security by adding a .dockerignore file, addressing the security risk of sensitive files being leaked into Docker images. However, the current approach of ignoring all files (*) is too broad and breaks existing Docker builds that rely on the local build context, such as dev.Dockerfile. It is recommended to adopt a more selective .dockerignore using an allowlist approach to protect sensitive data without disrupting other build processes.

[gemini-code-assist]

The current * in .dockerignore ignores all files, causing a denial of service for development and tooling build pipelines by breaking Dockerfiles like dev.Dockerfile, docker/bitcoind/Dockerfile, docker/btcd/Dockerfile, and tools/Dockerfile which rely on the build context. To prevent sensitive file leakage while maintaining build functionality, an allowlist approach is necessary. Please consider the suggested code_suggestion to allow only required files.

# ignore everything
*

# Allowlist files needed for other Dockerfiles
!docker/lnd/start-lnd.sh
!docker/bitcoind/start-bitcoind.sh
!docker/btcd/start-btcctl.sh
!docker/btcd/start-btcd.sh
!tools/
!lnrpc/
!make/
# Add other necessary source files for dev.Dockerfile if needed
#!.git/
#!*

[schildbach]

I force-pushed a new version that takes dev.Dockerfile into account.

However I wasn't able to test the resulting output properly as I'm not an LND dev. So this should be reviewed carefully wether any important files are missing (and its non-existence silently ignored by the Makefile).

[schildbach]

@schildbach, remember to re-request review from reviewers when ready

How do I do that? I don't think I have permission to (re)request review.

[lightninglabs-deploy]

@schildbach, remember to re-request review from reviewers when ready