● Covered by 1 source · 1 reportLow impact1 neutral
Git Commit Size Varies Based on Content Compressibility and Repository State
Key points
- Git stores data as zlib compressed objects.
- Packfiles further reduce redundancy across objects.
- Small changes incur kilobytes of overhead.
- Large files can be stored at 10-50% of original size.
Git's Storage Mechanism
Git stores data as "objects" which are compressed using zlib. The exact size of a commit is influenced by the compressibility of the files, which relates to the amount of repetition within their content. This compression is a fundamental aspect of how Git manages repository size.
Efficiency with Packfiles
Beyond individual object compression, Git enhances storage efficiency by converting object files into "packfiles." This process eliminates redundancy across multiple objects, leading to additional space savings. The use of packfiles is a key factor in Git's ability to manage large repositories effectively over time.
Experimental Findings on Commit Size
Experiments conducted with loose objects (before packfile creation) illustrate the varying sizes of Git commits. An empty Git repository (`git init`) starts at approximately 64,828 bytes. Committing 250 tiny files added about 47,640 bytes. A 3-byte change to a file in a 50-file directory added 17,145 bytes, while the same 3-byte change in a single-file repository added 8,709 bytes.
Committing a 583,840-byte binary file resulted in 297,873 bytes of storage, and a 16,415,223-byte source file required 1,622,188 bytes. These results indicate that even very tiny commits incur kilobytes of overhead, with the exact amount depending on the size of the file or directory tree involved in the changes. For larger commits with few files, the stored data in `.git` can range from 10% to 50% of the uncompressed committed files, demonstrating Git's storage efficiency.
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Reporting from
The size of a Git commit depends on the compressibility of the files and whether objects are stored loosely or in packfiles. Experiments show that even small changes incur kilobytes of overhead, while larger files can be stored with significant efficiency due to Git's compression methods.