Why Git LFS Repos Can Be Larger: A Guide

Understanding Git LFS Repository Size

In the process of migrating a large SVN repository to Git, I encountered an interesting issue. When converting the Git repository to use Git LFS for storing binaries, the size of the repository increased significantly.

This article explores why the Git LFS migrated repository ends up larger than the original, and whether regular Git packs binaries more efficiently than Git LFS. I will also share the steps and commands used during the migration process.

Understanding the Migration Scripts

The Bash script is designed to automate the migration of a Git repository to use Git LFS. First, it initializes LFS and tracks binary files with the git lfs track command. Then, it adds the tracking configuration to the repository and commits it. The bfg --convert-to-git-lfs command is used to convert existing binary files in the repository to LFS, effectively removing them from the main Git history. After this conversion, the script runs git reflog expire and git gc --prune=now to expire old references and prune unnecessary files, reducing the repository size.

The Python script complements this by providing a way to compare the repository sizes before and after migration. Using the subprocess.run function, it executes the du -sh command to get the disk usage of specified directories. This allows for a clear comparison of the repository sizes pre- and post-LFS migration. The output helps understand the impact of the migration and cleanup commands on the repository size, verifying the effectiveness of the migration process.

Automating Git LFS Migration and Cleanup Process

Bash Script for Git LFS Migration and Cleanup

#!/bin/bash
# Step 1: Initialize LFS and track file type
git lfs install
git lfs track "*.bin"
git add .gitattributes
git commit -m "Track binary files with LFS"
# Step 2: Migrate existing files to LFS
bfg --convert-to-git-lfs '*.bin' --no-blob-protection
git reflog expire --expire=now --all
git gc --prune=now --aggressive

Analyzing Repository Size Changes Post-Migration

Python Script for Repository Size Comparison

import subprocess
def get_repo_size(path):
    result = subprocess.run(['du', '-sh', path], stdout=subprocess.PIPE)
    size = result.stdout.split()[0].decode('utf-8')
    return size
before_migration = get_repo_size('/path/to/repo_before_lfs')
after_migration = get_repo_size('/path/to/repo_after_lfs')
print(f"Size before LFS migration: {before_migration}")
print(f"Size after LFS migration: {after_migration}")

Exploring the Impact of Git LFS on Repository Size

One important aspect of migrating to Git LFS is understanding the differences in how Git and Git LFS handle file storage. Git LFS replaces large files in your repository with small pointer files, while the actual file contents are stored separately. This separation can cause the on-disk size to increase temporarily during migration due to the presence of both the original large files and the new LFS pointers. Another factor is that Git LFS uses different compression and storage mechanisms, which may not always result in smaller repository sizes, especially immediately after migration.

To optimize the repository size post-migration, it's crucial to run commands like git reflog expire and git gc --prune=now --aggressive. These commands help remove unnecessary files and references, significantly reducing the repository size. It's also important to monitor the repository's size over time and perform regular maintenance to keep it optimized. Understanding these nuances can help manage expectations and ensure an efficient migration process.

Common Questions About Git LFS Migration

1. Why does the repository size increase after initial Git LFS migration?
2. The increase is due to the presence of both original files and LFS pointers. Running git gc commands helps reduce this size.
3. What does git reflog expire do?
4. This command removes outdated reflog entries, helping to clean up the repository and free up space.
5. How does bfg --convert-to-git-lfs work?
6. It converts existing large files to use Git LFS, effectively moving them out of the main Git history.
7. Why is git gc --prune=now --aggressive used?
8. This command aggressively cleans up unnecessary files and optimizes repository storage.
9. What is the benefit of using Git LFS?
10. Git LFS reduces the size of repository clones by storing large files separately, improving performance.
11. Can the repository size be reduced immediately after migration?
12. Yes, by running git reflog expire and git gc commands to remove unnecessary data.
13. Is there a risk of data loss when using Git LFS?
14. No, as long as the migration and cleanup commands are run correctly, the data remains intact.
15. How often should maintenance commands be run?
16. It's advisable to run maintenance commands regularly, especially after significant changes to the repository.

Final Thoughts on Git LFS Migration

The migration to Git LFS can result in a temporary increase in repository size due to the coexistence of original files and LFS pointers. However, running maintenance commands such as git reflog expire and git gc --prune=now --aggressive can significantly reduce the size. Understanding the differences in how Git and Git LFS handle file storage is crucial for effective migration.

While the initial size increase might be concerning, the long-term benefits of using Git LFS, especially for remote storage and cloning efficiency, outweigh the temporary downsides. Regular maintenance and proper configuration can ensure an optimized and manageable repository size.