Git (version control)
Git is a distributed version control system created by Linus Torvalds in 2005 for Linux kernel development. It models a repository as a content-addressed object database — blobs, trees, commits, and tags — identified by cryptographic hash.
Git (version control)|Git is a free and open-source distributed version control system created by Linus Torvalds in April 2005 to manage the Linux kernel source tree after the project lost access to the proprietary BitKeeper tool it had been using. Torvalds wrote the initial implementation in roughly ten days; maintenance was soon handed off to Junio Hamano, who has led the project ever since. Git's core design is a Content-Addressable Storage object database. Every artifact in a repository — a file (a blob), a directory snapshot (a tree), a commit pointing to a tree plus parent commits, or a signed tag — is stored as an object identified by the Cryptographic Hash Function of its contents. The history therefore forms an immutable Merkle Tree in which any change to any byte propagates new hashes all the way to the commit, making tampering self-evident. Branches and tags are simply human-readable pointers into this graph. Because every clone contains the full object database and history, Git is genuinely distributed: developers commit, branch, and merge locally, then exchange objects with other repositories using push and fetch. Originally Git used SHA-1 as the object hash, but in late 2018 the project selected SHA-256 as the successor algorithm because of demonstrated collision attacks against SHA-1; a transition plan supports interoperability between SHA-1 and SHA-256 repositories during the long migration. As of the mid-2020s Git is by a wide margin the most widely used version control system in software development, and is the substrate for hosting platforms such as GitHub, GitLab, and Bitbucket.