Git/GitLab – Reject Commits with Raw Binary Files Instead of LFS Pointer Files: A Step-by-Step Guide

Are you tired of dealing with large binary files clogging up your Git repository? Do you want to ensure that your team only commits LFS (Large File Storage) pointer files instead of raw binary files? Look no further! In this article, we’ll show you how to configure Git and GitLab to reject commits with raw binary files, promoting a cleaner and more efficient repository.

Why is this important?

Raw binary files can cause a host of problems in your Git repository, including:

• Spike in repository size, making clones and fetches slower
• Difficulty in tracking changes and managing versions
• Inefficient use of storage space
• Potential security risks from storing sensitive files

By using LFS pointer files, you can keep your repository lean and mean, while storing large files in a separate, more suitable location. But how do you ensure that your team only commits LFS pointer files?

Configuring Git

The first step is to configure Git to reject commits with raw binary files. You can do this by creating a Git hook. A Git hook is a script that runs at specific points in the Git workflow, allowing you to automate tasks and enforce policies.

Creating a pre-commit hook

Create a new file called `pre-commit` in the `.git/hooks` directory of your repository. This file should have execute permissions (chmod +x .git/hooks/pre-commit). Then, add the following code:

#!/bin/sh

# Check for raw binary files
for file in `git diff --cached --name-only --diff-filter=ACMRTUXB`
do
  if [ ! -LT "$file" ]; then
    echo "Error: Raw binary file detected: $file"
    exit 1
  fi
done

This script uses the `git diff` command to list all files in the commit, and then checks if each file is a raw binary file using the `-LT` test. If a raw binary file is found, the script exits with an error code, preventing the commit from completing.

Configuring GitLab

While the pre-commit hook is a great start, it’s not foolproof. A determined user could still push raw binary files to the repository. To add an extra layer of protection, you can configure GitLab to reject pushes with raw binary files.

Creating a GitLab CI/CD pipeline

Create a new file called `.gitlab-ci.yml` in the root of your repository. This file will define a GitLab CI/CD pipeline that runs on every push. Add the following code:

stages:
  - check-binary-files

check-binary-files:
  stage: check-binary-files
  script:
    - git ls-files --cached --others --exclude-from=.gitignore --error-unmatch -- | xargs -I {} bash -c '[ ! -LT "{}" ] && echo "Error: Raw binary file detected: {}" && exit 1'

This pipeline uses the `git ls-files` command to list all files in the commit, and then checks if each file is a raw binary file using the same `-LT` test as before. If a raw binary file is found, the pipeline exits with an error code, preventing the push from completing.

Testing and Refining

Now that you’ve configured Git and GitLab, it’s time to test your setup. Try committing a raw binary file and pushing it to the repository. You should see an error message indicating that the push was rejected.

If you find that the hook or pipeline is not catching all raw binary files, you may need to refine your approach. Here are some additional tips:

• Use a more sophisticated file type detection algorithm, such as `file` command
• Add exceptions for specific file types or directories that should be allowed
• Configure the hook and pipeline to only run on specific branches or repositories

File Type	Allowed	Action
Image files (jpg, png, etc.)	Yes	Allow
Executable files (exe, bin, etc.)	No	Reject
Large text files (log, dump, etc.)	No	Reject

Best Practices

To get the most out of this setup, follow these best practices:

1. Use LFS for large files: Make sure your team understands the importance of using LFS for large files. Provide training and resources to help them get started.
2. Configure exceptions carefully: Be cautious when adding exceptions to your hook and pipeline. Make sure you’re not inadvertently allowing raw binary files to slip through.
3. Monitor and refine: Regularly monitor your repository for raw binary files and refine your hook and pipeline as needed.
4. Communicate with your team: Make sure your team understands the reasons behind this setup and the benefits it brings to your repository.

By following these steps and best practices, you can ensure that your Git repository remains clean and efficient, with LFS pointer files taking the place of raw binary files.

Conclusion

In this article, we’ve shown you how to configure Git and GitLab to reject commits with raw binary files, promoting a cleaner and more efficient repository. By using LFS pointer files and enforcing this policy through hooks and pipelines, you can ensure that your team only commits files that are suitable for version control. Remember to test and refine your setup regularly, and communicate with your team to ensure a smooth transition.

Happy coding, and may your repository be forever free of raw binary files!

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