Understanding Git Repository Size: Why Is It Smaller Than My Original Files?

Are you puzzled by the difference in size between your original files and your Git repository? If you've ever wondered why your Git repository seems much smaller than the folder you copied it from, you're not alone. In this blog post, we'll demystify this phenomenon and explain why Git repositories are typically smaller than the original files they contain.

What is Git?

Before diving into the specifics, let's briefly review what Git is and how it works. Git is a version control system widely used by developers to track changes in their codebase. It allows users to maintain a history of changes, collaborate with others, and manage different versions of their projects.

How Git Stores Data / How Git Stores Changes (Not Entire Files)

Unlike traditional file storage systems, Git doesn't store each file individually. Instead, it employs a unique approach to track changes called "snapshot-based" version control. Git stores snapshots of your project's entire filesystem at different points in time, allowing you to navigate through the history and revert to previous states. Diffs and Deltas: The key to Git's magic is that it doesn't simply store a snapshot of your entire project at each commit. Instead, it records the changes (diffs or deltas) between subsequent versions of files. This difference-based approach is highly space-efficient.

Example: Imagine editing a text file. If you only change a single line, Git stores the modified line, not a whole new copy of the file.

The Working Directory vs. the .git Folder

Working Directory: This holds the currently checked-out version of your project files. These files are uncompressed, readily available for editing.

.git Folder: Inside every Git repository is a hidden .git folder. This is where the real magic happens. Git stores all the version history, compressed objects, and data needed to manage your project.

The Influence of File Types

Text-based files: Files containing plain text (code, configuration files) compress remarkably well. Git shines when handling these file types.

Binary files: Large images, videos, or executables usually aren't compressible. Each modification might force Git to store a nearly complete new version of the file, potentially increasing the repository size.

Compression and Delta Storage

One of the key reasons for the smaller size of Git repositories is compression. When you push code to a Git repository, Git compresses the files using various compression techniques. This compression reduces the overall size of the repository by eliminating redundant data and optimizing storage.

Additionally, Git uses delta compression to store only the changes (or "deltas") between files, rather than storing each file in its entirety every time it changes. This approach significantly reduces the amount of storage required, especially for files with repetitive content or frequent modifications.

Strategies for Managing Repo Size

Large Binary Files: Consider using Git Large File Storage (Git LFS) for handling huge binary files. Git LFS stores pointers to these files instead of the full files themselves.

Cleaning History: If your repository accumulates a lot of history, use features like git gc (garbage collection) or git rebase to clean up and repack your repository. Be careful though, as some of these operations can alter commit history.

Example: Text-Based Files

Let's illustrate this with an example. Imagine you have a folder containing several text files, each with some repetitive content. When you copy this folder to another location using a tool like rsync, the files are transferred as-is, maintaining their original size.

However, when you initialize a Git repository and add these files to it, Git employs compression and delta storage techniques. It compresses the files and stores them as a series of snapshots, capturing only the changes between versions. As a result, the size of the Git repository is often much smaller than the original folder.

Optimization Techniques / Compression Techniques

In addition to compression and delta storage, Git employs various optimization techniques to further reduce repository size. These include:

• Packing objects: Git packs multiple objects (e.g., files, commits) into "pack files," which are more space-efficient than storing each object individually.

• Deduplication: Git identifies and removes duplicate data across different versions of files, saving storage space.

• Binary deltas: Git can efficiently store binary files by generating binary deltas, which represent only the changes between versions.

• Loose Objects: Initially, Git might store objects individually, but over time, it uses a process called "packing" to consolidate them into efficient packfiles.

Conclusion

In summary, the smaller size of Git repositories compared to the original files is due to compression, delta storage, and optimization techniques employed by Git. By storing snapshots of changes and efficiently managing data, Git ensures that version control remains lightweight and scalable.

Next time you notice the size difference between your files and your Git repository, remember that Git's clever storage mechanisms are at work, making version control efficient and space-saving.

Understanding Git's storage mechanisms can help you appreciate the power and elegance of this essential tool for software development.