Git () is a distributed version control system that tracks changes in any set of computer files, usually used for coordinating work among programmers collaboratively developing source code during software development. Its goals include speed, data integrity, and support for distributed, non-linear workflows (thousands of parallel branches running on different systems). Git was originally authored by Linus Torvalds in 2005 for development of the Linux kernel, with other kernel developers contributing to its initial development. Since 2005, Junio Hamano has been the core maintainer. As with most other distributed version control systems, and unlike most client–server systems, every Git directory on every computer is a full-fledged repository with complete history and full version-tracking abilities, independent of network access or a central server. Git is free and open-source software distributed under the GPL-2.0-only license. History Git development began in April 2005, after many developers of the Linux kernel gave up access to BitKeeper, a proprietary source-control management (SCM) system that they had been using to maintain the project since 2002. The copyright holder of BitKeeper, Larry McVoy, had withdrawn free use of the product after claiming that Andrew Tridgell had created SourcePuller by reverse engineering the BitKeeper protocols. The same incident also spurred the creation of another version-control system, Mercurial. Linus Torvalds wanted a distributed system that he could use like BitKeeper, but none of the available free systems met his needs. Torvalds cited an example of a source-control management system needing 30 seconds to apply a patch and update all associated metadata, and noted that this would not scale to the needs of Linux kernel development, where synchronizing with fellow maintainers could require 250 such actions at once. For his design criterion, he specified that patching should take no more than three seconds, and added three more goals: Take Concurrent Versions System (CVS) as an example of what not to do; if in doubt, make the exact opposite decision. Support a distributed, BitKeeper-like workflow. Include very strong safeguards against corruption, either accidental or malicious. These criteria eliminated every version-control system in use at the time, so immediately after the 2.6.12-rc2 Linux kernel development release, Torvalds set out to write his own. The development of Git began on 3 April 2005. Torvalds announced the project on 6 April and became self-hosting the next day. The first merge of multiple branches took place on 18 April. Torvalds achieved his performance goals; on