Git 2.51 Launches with Enhanced Performance Optimizations and SHA-256 as the Default Hash Function
Git 2.51.0 has been officially released following an accelerated eight-week development cycle, introducing significant performance improvements and security enhancements that lay the groundwork for the upcoming Git 3.0 major release. The latest version delivers substantial speed improvements for core Git operations, implementing SHA-256 as the default hash function and introducing the reftable format as the new reference backend standard. Key takeaways include a 22x speed increase for git-fetch and an 18x speed increase for git-push through batched updates in large repositories. The new batched update system consolidates multiple reference updates under a single transaction, significantly reducing overhead, especially in repositories with extensive reference collections, such as monorepos or complex CI/CD environments. For repositories containing 10,000 references, git-fetch demonstrates a 22x performance improvement for the reftable backend and a 1.25x improvement for the files backend, while git-push shows an 18x improvement for the reftable backend and a 1.21x improvement for the files backend.
In addition to performance enhancements, Git 2.51.0 marks the transition to SHA-256 as the default hash algorithm, replacing the aging SHA-1 implementation. This change addresses critical security vulnerabilities, particularly the SHAttered attack that demonstrated practical SHA-1 hash collisions. While Git has employed a hardened SHA-1 implementation since version 2.13.0, the move to SHA-256 ensures robust long-term security for Git’s content-addressable filesystem. The release also introduces the reftable format as the default reference backend for Git 3.0, resolving multiple limitations of the traditional files backend. The reftable system addresses case-sensitivity issues on Windows and macOS platforms, eliminates Unicode normalization problems, and provides atomic reference transactions. Furthermore, it utilises geometric compaction for superior performance and reduced storage requirements through a binary format.
Categories: Performance Improvements, Security Enhancements, Reference Backend Updates
Tags: Git, Release, Performance, SHA-256, Hash, Reftable, Backend, Optimization, Security, Transactions