Array ( [0] => {{Short description|Software for version control of files}} [1] => {{Other uses|Git (disambiguation)}} [2] => {{distinguish|GitHub|GitLab|Gitea}} [3] => {{Use dmy dates|date=September 2020}} [4] => {{Infobox software [5] => | name = Git [6] => | logo = [[File:Git-logo-2012.svg|150px]] [7] => | screenshot = Git session.svg [8] => | caption = A command-line session showing repository creation, addition of a file, and remote synchronization [9] => | author = [[Linus Torvalds]]{{cite web [10] => | url = https://github.com/git/git/commit/e83c5163316f89bfbde7d9ab23ca2e25604af290 [11] => | date = 8 April 2005 [12] => | title = Initial revision of "git", the information manager from hell [13] => | publisher = [[GitHub]] [14] => | access-date = 20 December 2015 [15] => | url-status = live [16] => | archive-url = https://web.archive.org/web/20151116175401/https://github.com/git/git/commit/e83c5163316f89bfbde7d9ab23ca2e25604af290 [17] => | archive-date = 16 November 2015}} [18] => | developer = Junio Hamano and others{{cite web [19] => | url = https://github.com/git/git/graphs/contributors [20] => | date = 8 June 2016 [21] => | title = Commit Graph [22] => | publisher = [[GitHub]] [23] => | access-date = 19 December 2015 [24] => | url-status = live [25] => | archive-url = https://web.archive.org/web/20160120121816/https://github.com/git/git/graphs/contributors [26] => | archive-date = 20 January 2016}} [27] => | released = {{Start date and age|2005|4|7|df=yes}} [28] => | latest release version = {{wikidata|property|preferred|references|edit|Q186055|P348|P548=Q2804309}} [29] => | latest release date = {{wikidata|qualifier|preferred|single|Q186055|P348|P548=Q2804309|P577}} [30] => | latest preview version = {{wikidata|property|preferred|references|edit|Q186055|P348|P548=Q51930650}} [31] => | latest preview date = {{wikidata|qualifier|preferred|single|Q186055|P348|P548=Q51930650|P577}} [32] => | programming language = Primarily in [[C (programming language)|C]], with [[GUI]] and [[Scripting language|programming scripts]] written in [[Shell script]], [[Perl]], [[Tcl]] and [[Python (programming language)|Python]]{{cite web |title=Git website |url=https://git-scm.com/about/small-and-fast |access-date=9 June 2022 |archive-url=https://web.archive.org/web/20220609042334/https://git-scm.com/about/small-and-fast |archive-date=9 June 2022 |url-status=live}}{{cite web |title=Git Source Code Mirror |url=https://github.com/git/git |website=[[GitHub]] |access-date=9 June 2022 |archive-url=https://web.archive.org/web/20220603081319/https://github.com/git/git |archive-date=3 June 2022 |url-status=live}} [33] => | operating system = [[POSIX]] ([[Linux]], [[macOS]], [[Solaris (operating system)|Solaris]], [[AIX]]), [[Microsoft Windows|Windows]] [34] => | size = [35] => | language = English [36] => | genre = [[Version control]] [37] => | license = [[GNU General Public License|GPL-2.0-only]]{{efn-lr|GPL-2.0-only since 2005-04-11. Some parts under compatible licenses such as [[GNU Lesser General Public License|LGPLv2.1]].{{cite web [38] => | url = https://github.com/git/git/blob/master/LGPL-2.1 [39] => | title = Git's LGPL license at github.com [40] => | date = 20 May 2011 [41] => | website = [[GitHub]] [42] => | access-date = 12 October 2014 [43] => | url-status = live [44] => | archive-url = https://web.archive.org/web/20160411135049/https://github.com/git/git/blob/master/LGPL-2.1 [45] => | archive-date = 11 April 2016}}}}{{cite web [46] => | url = https://github.com/git/git/blob/master/COPYING [47] => | title = Git's GPL license at github.com [48] => | date = 18 January 2010 [49] => | website = [[GitHub]] [50] => | access-date = 12 October 2014 [51] => | url-status = live [52] => | archive-url = https://web.archive.org/web/20160411135124/https://github.com/git/git/blob/master/COPYING [53] => | archive-date = 11 April 2016}} [54] => | standard = [55] => | AsOf = [56] => }} [57] => [58] => '''Git''' ({{IPAc-en|g|ɪ|t}}){{cite web |url = https://www.youtube.com/watch?v=4XpnKHJAok8&t=1m30s |title = Tech Talk: Linus Torvalds on git (at 00:01:30) |via = YouTube |access-date = 2014-07-20 |url-status = live |archive-url = https://web.archive.org/web/20151220133030/https://www.youtube.com/watch?v=4XpnKHJAok8&t=1m30s |archive-date = 20 December 2015}} is a [[distributed version control]] system{{sfn | Chacon | Straub | 2014 | pp=29-31}} that tracks changes in any set of [[computer file]]s, usually used for coordinating work among programmers who are collaboratively developing [[source code]] during [[software development]]. [59] => [60] => Git's goals include speed, [[data integrity]], and support for [[Distributed computing|distributed]], non-linear workflows (thousands of parallel [[Branching (version control)|branches]] running on different computers).{{cite mailing list |mailing-list = linux-kernel |last = Torvalds |first = Linus |url = https://marc.info/?l=linux-kernel&m=111288700902396 |title = Re: Kernel SCM saga.. |date = 2005-04-07 |access-date = 3 February 2017 |archive-date = 1 July 2019 |archive-url = https://web.archive.org/web/20190701210808/https://marc.info/?l=linux-kernel |url-status = live }} "So I'm writing some scripts to try to track things a whole lot faster."{{cite mailing list |last = Torvalds |first = Linus |author-link = Linus Torvalds |mailing-list = git |date = 2007-06-10 |title = Re: fatal: serious inflate inconsistency |url = https://marc.info/?l=git&m=118143549107708}}{{cite video |people = Linus Torvalds |date = 2007-05-03 |url = https://www.youtube.com/watch?v=4XpnKHJAok8 |title = Google tech talk: Linus Torvalds on git |time = 02:30 |access-date = 2007-05-16 |url-status = live |archive-url = https://web.archive.org/web/20070528041814/http://www.youtube.com/watch?v=4XpnKHJAok8 |archive-date = 28 May 2007}} Git was originally authored by [[Linus Torvalds]] in 2005 for the development of the [[Linux kernel]], with other kernel developers contributing to its initial development.{{cite book |chapter-url = https://git-scm.com/book/en/v2/Getting-Started-A-Short-History-of-Git |chapter = A Short History of Git |title = Pro Git |publisher = Apress |access-date = 26 December 2015 |date = 2014 |edition = 2nd |url = https://git-scm.com/book/en/v2 |url-status = live |archive-url = https://web.archive.org/web/20151225223054/http://git-scm.com/book/en/v2 |archive-date = 25 December 2015}} It was prompted by the revocation of the free license of [[BitKeeper]], the proprietary source-control management system used for Linux kernel development since 2002. Since 2005, Junio Hamano has been the core maintainer of Git. As with most other distributed version control systems, and unlike most [[client–server]] systems, every Git [[directory (computing)|directory]] on every computer is a full-fledged [[Repository (version control)|repository]] with complete history and full version-tracking abilities, independent of [[Computer network|network]] access or a central [[Server (computing)|server]].{{cite book |last1 = Chacon |first1 = Scott |title = Pro Git |date = 24 December 2014 |publisher = [[Apress]] |location = New York, NY |isbn = 978-1-4842-0077-3 |pages = 29–30 |edition = 2nd |url = https://git-scm.com/book/en/v2 |url-status = live |archive-url = https://web.archive.org/web/20151225223054/http://git-scm.com/book/en/v2 |archive-date = 25 December 2015}} Git is a [[free and open-source software]] shared under the [[GNU General Public License|GPL-2.0-only license]]. [61] => [62] => Git's design benefits from Torvalds' experience with Linux and file-system performance, leading to features such as support for non-linear development, efficient handling of large projects, and [[cryptographic]] authentication of history. Its toolkit-based design allows for pluggable merge strategies and flexibility in managing version control tasks. Despite its comprehensive feature set, Git has faced security challenges, leading to updates and patches that address vulnerabilities. The trademark "Git" is registered by the [[Software Freedom Conservancy]], marking its official recognition and continued evolution in the [[open-source]] community. [63] => [64] => Git's adoption has grown rapidly, becoming the most popular distributed version control system, with nearly 95% of developers reporting it as their primary version control system as of 2022. It is the most widely used source-code management tool among professional developers. There are offerings of Git repository services, including [[GitHub]], [[SourceForge]], [[Bitbucket]] and [[GitLab]].{{cite web |last=Krill |first=Paul |date=28 September 2016 |title=Enterprise repo wars: GitHub vs. GitLab vs. Bitbucket |url=https://www.infoworld.com/article/3123244/enterprise-repo-wars-github-vs-gitlab-vs-bitbucket.html |access-date=2 February 2020 |website=InfoWorld}} [65] => [66] => ==History== [67] => Git development was started by Torvalds in April 2005 when the proprietary [[Version control|source-control management]] (SCM) system used for Linux kernel development since 2002, [[BitKeeper]], revoked its free [[Software license|license]] for Linux development.{{cite news |last=Brown |first=Zack |date=2018-07-27 |title=A Git Origin Story |work=Linux Journal |publisher=Linux Journal |url=https://www.linuxjournal.com/content/git-origin-story |url-status=live |access-date=2020-05-28 |archive-url=https://web.archive.org/web/20200413113107/https://www.linuxjournal.com/content/git-origin-story |archive-date=2020-04-13}}{{Cite web |date=2005-04-11 |title=BitKeeper and Linux: The end of the road? |url=https://www.linux.com/news/bitkeeper-and-linux-end-road/ |access-date=2023-05-18 |website=Linux.com |language=en-US}} The copyright holder of BitKeeper, [[Larry McVoy]], claimed that [[Andrew Tridgell]] had created [[SourcePuller]] by [[reverse engineering]] the BitKeeper [[Communication protocol|protocols]].{{cite news |last= McAllister |first= Neil |url= http://www.infoworld.com/article/2670360/operating-systems/linus-torvalds--bitkeeper-blunder.html |title= Linus Torvalds' BitKeeper blunder |work= InfoWorld |date= 2005-05-02 |access-date= 2015-09-08 |url-status= live |archive-url= https://web.archive.org/web/20150826064920/http://www.infoworld.com/article/2670360/operating-systems/linus-torvalds--bitkeeper-blunder.html |archive-date= 26 August 2015}} The same incident also spurred the creation of another version-control system, [[Mercurial]]. [68] => [69] => Torvalds wanted a distributed system that he could use like BitKeeper, but none of the available free systems met his needs. He 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: [70] => * Take the [[Concurrent Versions System]] (CVS) as an example of what ''not'' to do; if in doubt, make the exact opposite decision. [71] => * Support a distributed, [[BitKeeper]]-like workflow. [72] => * Include very strong safeguards against corruption, either accidental or malicious. [73] => [74] => 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. [75] => [76] => The development of Git began on 3 April 2005.{{cite mailing list |url=https://marc.info/?l=git&m=117254154130732 |title=Re: Trivia: When did git self-host? |date=2007-02-27 |last=Torvalds |first=Linus |mailing-list=git}} Torvalds announced the project on 6 April and became [[Self-hosting (compilers)|self-hosting]] the next day.{{cite mailing list |url=https://marc.info/?l=linux-kernel&m=111280216717070 |title=Kernel SCM saga.. |date=2005-04-06 |last=Torvalds |first=Linus |mailing-list=linux-kernel}} The first merge of multiple branches took place on 18 April.{{cite mailing list |url=https://marc.info/?l=git&m=111377572329534 |title=First ever real kernel git merge! |date=2005-04-17 |last=Torvalds |first=Linus |mailing-list=git}} Torvalds achieved his performance goals; on 29 April, the nascent Git was benchmarked recording patches to the Linux kernel tree at a rate of 6.7 patches per second.{{cite mailing list |url=https://marc.info/?l=git&m=111475459526688 |title=Mercurial 0.4b vs git patchbomb benchmark |date=2005-04-29 |last=Mackall |first=Matt |mailing-list=git}} On 16 June, Git managed the kernel 2.6.12 release.{{cite mailing list |url=https://marc.info/?l=git-commits-head&m=111904216911731 |title=Linux 2.6.12 |date=2005-06-17 |last=Torvalds |first=Linus |mailing-list=git-commits-head}} [77] => [78] => Torvalds turned over [[software maintenance|maintenance]] on 26 July 2005 to Junio Hamano, a major contributor to the project.{{cite mailing list |url=https://marc.info/?l=git&m=112243466603239 |title=Meet the new maintainer.. |date=2005-07-27 |last=Torvalds |first=Linus |mailing-list=git}} Hamano was responsible for the 1.0 release on 21 December 2005.{{cite mailing list |url=https://marc.info/?l=git&m=113515203321888 |title=Announce: Git 1.0.0 |date=2005-12-21 |last=Hamano |first=Junio C. |mailing-list=git}} [79] => [80] => ===Naming=== [81] => Torvalds sarcastically quipped about the name ''git'' (which means "unpleasant person" in [[British English]] slang): "I'm an egotistical bastard, and I name all my projects after myself. First '[[Linux kernel|Linux]]', now 'git'."{{cite web [82] => | url = https://git.wiki.kernel.org/index.php/GitFaq#Why_the_.27Git.27_name.3F [83] => | title = GitFaq: Why the 'Git' name? [84] => | publisher = Git.or.cz [85] => | access-date = 2012-07-14 [86] => | url-status = live [87] => | archive-url = https://web.archive.org/web/20120723224559/https://git.wiki.kernel.org/index.php/GitFaq#Why_the_.27Git.27_name.3F [88] => | archive-date = 23 July 2012}}{{cite web |url= http://www.pcworld.idg.com.au/article/129776/after_controversy_torvalds_begins_work_git_/ |title= After controversy, Torvalds begins work on 'git' |date= 2012-07-14 |work= PC World |quote= [[Torvalds]] seemed aware that his decision to drop BitKeeper would also be controversial. When asked why he called the new software, 'git', [[British English|British]] slang meaning 'a rotten person', he said. 'I'm an egotistical bastard, so I name all my projects after myself. First Linux, now git.' |url-status= live |archive-url= https://web.archive.org/web/20110201184934/http://www.pcworld.idg.com.au/article/129776/after_controversy_torvalds_begins_work_git_/ |archive-date= 1 February 2011}} The [[man page]] describes Git as "the stupid content tracker".{{cite web |url= https://git-scm.com/docs/git.html |title= git(1) Manual Page |access-date= 2012-07-21 |url-status= live |archive-url= https://web.archive.org/web/20120621133627/http://www.git-scm.com/docs/git.html |archive-date= 21 June 2012}} [89] => [90] => The [[README|read-me file]] of the source code elaborates further:{{cite web |title= Initial revision of 'git', the information manager from hell · git/git@e83c516 |url= https://github.com/git/git/blob/e83c5163316f89bfbde7d9ab23ca2e25604af290/README |website= GitHub |access-date= 2016-01-21 |url-status= live |archive-url= https://web.archive.org/web/20171008211145/https://github.com/git/git/blob/e83c5163316f89bfbde7d9ab23ca2e25604af290/README |archive-date= 8 October 2017}} [91] => [92] => {{quote|"git" can mean anything, depending on your mood. [93] => * Random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant. [94] => * Stupid. Contemptible and despicable. Simple. Take your pick from the dictionary of slang. [95] => * "Global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room. [96] => * "Goddamn idiotic truckload of sh*t": when it breaks. [97] => }} [98] => [99] => The source code for Git refers to the program as "the information manager from hell". [100] => [101] => ===Characteristics=== [102] => Git's design is a synthesis of Torvalds's experience with Linux in maintaining a large distributed development project, along with his intimate knowledge of file-system performance gained from the same project and the urgent need to produce a working system in short order. These influences led to the following implementation choices: [103] => ; Strong support for non-linear development: Git supports rapid branching and merging, and includes specific tools for visualizing and navigating a non-linear development history. In Git, a core assumption is that a change will be merged more often than it is written, as it is passed around to various reviewers. In Git, branches are very lightweight: a branch is only a reference to one commit. [104] => ; Distributed development: Like [[Darcs]], [[BitKeeper]], [[Mercurial]], [[Bazaar (software)|Bazaar]], and [[Monotone (software)|Monotone]], Git gives each developer a local copy of the full development history, and changes are copied from one such repository to another. These changes are imported as added development branches and can be merged in the same way as a locally developed branch.{{cite web |title=Git – Distributed Workflows |url=https://git-scm.com/book/en/v2/Distributed-Git-Distributed-Workflows |website=Git |access-date=15 June 2020 |archive-date=22 October 2014 |archive-url=https://web.archive.org/web/20141022020026/http://git-scm.com/book/en/Distributed-Git-Distributed-Workflows |url-status=live }} [105] => ; Compatibility with existing systems and protocols: Repositories can be published via [[HTTPS|Hypertext Transfer Protocol Secure]] (HTTPS), [[Hypertext Transfer Protocol]] (HTTP), [[File Transfer Protocol]] (FTP), or a Git protocol over either a plain socket or [[Secure Shell]] (ssh). Git also has a CVS server emulation, which enables the use of existing CVS clients and IDE plugins to access Git repositories. [[Apache Subversion|Subversion]] repositories can be used directly with git-svn.{{Cite web|last=Gunjal|first=Siddhesh|date=2019-07-19|title=What is Version Control Tool? Explore Git and GitHub|url=https://medium.com/analytics-vidhya/what-is-version-control-tool-explore-git-and-github-e8c4e719bc05|access-date=2020-10-25|website=Medium|language=en}} [106] => ; Efficient handling of large projects: Torvalds has described Git as being very fast and scalable,{{cite mailing list |last=Torvalds |first=Linus |url=https://marc.info/?l=git&m=116128307511686 |title=Re: VCS comparison table |date=2006-10-19 |mailing-list=git}} and performance tests done by MozillaJst's Blog on Mozillazine {{cite web|title=bzr/hg/git performance |url=http://weblogs.mozillazine.org/jst/archives/2006/11/vcs_performance.html |access-date=12 February 2015 |url-status=dead |archive-url=https://web.archive.org/web/20100529094107/http://weblogs.mozillazine.org/jst/archives/2006/11/vcs_performance.html |archive-date=29 May 2010}} showed that it was an [[order of magnitude]] faster diffing large repositories than [[Mercurial]] and [[GNU Bazaar]]; fetching version history from a locally stored repository can be one hundred times faster than fetching it from the remote server.{{cite web |last=Dreier |first=Roland |url=http://digitalvampire.org/blog/index.php/2006/11/16/oh-what-a-relief-it-is/ |title=Oh what a relief it is |date=2006-11-13 |url-status=live |archive-url=https://web.archive.org/web/20090116175841/http://digitalvampire.org/blog/index.php/2006/11/16/oh-what-a-relief-it-is/ |archive-date=16 January 2009}}, observing that "git log" is 100x faster than "svn log" because the latter must contact a remote server. [107] => ; Cryptographic authentication of history: The Git history is stored in such a way that the ID of a particular version (a ''commit'' in Git terms) depends upon the complete development history leading up to that commit. Once it is published, it is not possible to change the old versions without it being noticed. The structure is similar to a [[Merkle tree]], but with added data at the nodes and leaves.{{cite web |url=https://www.kernel.org/pub/software/scm/git/docs/user-manual.html#trust |work=Git Concepts |publisher=Git User's Manual |title=Trust |date=2006-10-18 |url-status=live |archive-url=https://web.archive.org/web/20170222053056/https://www.kernel.org/pub/software/scm/git/docs/user-manual.html#trust |archive-date=22 February 2017}} ([[Mercurial]] and [[Monotone (software)|Monotone]] also have this property.) [108] => ; Toolkit-based design: Git was designed as a set of programs written in [[C (programming language)|C]] and several shell scripts that provide wrappers around those programs.{{cite mailing list |mailing-list=git |last=Torvalds |first=Linus |url=https://marc.info/?l=git&m=116118369005954 |title=Re: VCS comparison table |access-date=2009-04-10}}, describing Git's script-oriented design Although most of those scripts have since been rewritten in C for speed and portability, the design remains, and it is easy to chain the components together.{{cite web |author=iabervon |url=https://lwn.net/Articles/165202/ |title=Git rocks! |date=2005-12-22 |url-status=live |archive-url=https://web.archive.org/web/20160914100946/https://lwn.net/Articles/165202/ |archive-date=14 September 2016}}, praising Git's scriptability. [109] => ; Pluggable merge strategies: As part of its toolkit design, Git has a well-defined model of an incomplete merge, and it has multiple algorithms for completing it, culminating in telling the user that it is unable to complete the merge automatically and that manual editing is needed.{{Cite web|title=Git – Git SCM Wiki|url=https://git.wiki.kernel.org/index.php/Git|access-date=2020-10-25|website=git.wiki.kernel.org}} [110] => ; [[Garbage (computer science)|Garbage]] accumulates until collected: Aborting operations or backing out changes will leave useless dangling objects in the database. These are generally a small fraction of the continuously growing history of wanted objects. Git will automatically perform [[garbage collection (computer science)|garbage collection]] when enough loose objects have been created in the repository. Garbage collection can be called explicitly using git gc.{{sfn | Chacon | Straub | 2014 | p=}}{{cite web |url=https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-gc.html |title=Git User's Manual |date=2020-03-10 |url-status=live |archive-url=https://web.archive.org/web/20200510190720/https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-gc.html |archive-date=10 May 2020}} [111] => ; Periodic explicit object packing: Git stores each newly created object as a separate file. Although individually compressed, this takes up a great deal of space and is inefficient. This is solved by the use of ''packs'' that store a large number of objects [[Delta encoding|delta-compressed]] among themselves in one file (or network byte stream) called a ''packfile''. Packs are compressed using the [[Heuristic (computer science)|heuristic]] that files with the same name are probably similar, without depending on this for correctness. A corresponding index file is created for each packfile, telling the offset of each object in the packfile. Newly created objects (with newly added history) are still stored as single objects, and periodic repacking is needed to maintain space efficiency. The process of packing the repository can be very computationally costly. By allowing objects to exist in the repository in a loose but quickly generated format, Git allows the costly pack operation to be deferred until later, when time matters less, e.g., the end of a workday. Git does periodic repacking automatically, but manual repacking is also possible with the git gc command.{{sfn | Chacon | Straub | 2014 | p=499}} For data integrity, both the packfile and its index have an [[SHA-1]] checksum{{sfn | Chacon | Straub | 2014 | pp=33-34}} inside, and the file name of the packfile also contains an SHA-1 checksum. To check the integrity of a repository, run the git fsck command.{{cite web |title=Git – Packfiles |url=https://git-scm.com/book/en/v2/Git-Internals-Packfiles |website=Git}}{{sfn | Chacon | Straub | 2014 | p=568}} [112] => [113] => Another property of Git is that it snapshots directory trees of files. The earliest systems for tracking versions of source code, [[Source Code Control System]] (SCCS) and [[Revision Control System]] (RCS), worked on individual files and emphasized the space savings to be gained from [[interleaved deltas]] (SCCS) or [[delta encoding]] (RCS) the (mostly similar) versions. Later revision-control systems maintained this notion of a file having an identity across multiple revisions of a project. However, Torvalds rejected this concept.{{cite mailing list |mailing-list=linux-kernel |last=Torvalds |first=Linus |url=https://marc.info/?l=linux-kernel&m=111314792424707 |title=Re: more git updates.. |date=2005-04-10}} Consequently, Git does not explicitly record file revision relationships at any level below the source-code tree. [114] => [115] => These implicit revision relationships have some significant consequences: [116] => * It is slightly more costly to examine the change history of one file than the whole project.{{cite mailing list |mailing-list=git |last=Haible |first=Bruno |url=https://marc.info/?l=git&m=117119479505638 |title=how to speed up 'git log'? |date=2007-02-11}} To obtain a history of changes affecting a given file, Git must walk the global history and then determine whether each change modified that file. This method of examining history does, however, let Git produce with equal efficiency a single history showing the changes to an arbitrary set of files. For example, a subdirectory of the source tree plus an associated global header file is a very common case. [117] => * Renames are handled implicitly rather than explicitly. A common complaint with [[Concurrent Versions System|CVS]] is that it uses the name of a file to identify its revision history, so moving or renaming a file is not possible without either interrupting its history or renaming the history and thereby making the history inaccurate. Most post-CVS revision-control systems solve this by giving a file a unique long-lived name (analogous to an [[inode]] number) that survives renaming. Git does not record such an identifier, and this is claimed as an advantage.{{cite mailing list |mailing-list=git |last=Torvalds |first=Linus |url=https://marc.info/?l=git&m=114123702826251 |title=Re: impure renames / history tracking |date=2006-03-01}}{{cite mailing list |mailing-list=git |last=Hamano |first=Junio C. |url=https://marc.info/?l=git&m=114316047119262 |title=Re: Errors GITtifying GCC and Binutils |date=2006-03-24}} [[Source code]] files are sometimes split or merged, or simply renamed,{{cite mailing list |mailing-list=git |last=Hamano |first=Junio C. |url=https://marc.info/?l=git&m=114315795227271 |title=Re: Errors GITtifying GCC and Binutils |date=2006-03-23}} and recording this as a simple rename would freeze an inaccurate description of what happened in the (immutable) history. Git addresses the issue by detecting renames while browsing the history of snapshots rather than recording it when making the snapshot.{{cite mailing list |mailing-list=git |last=Torvalds |first=Linus |url=https://marc.info/?l=git&m=116473016012824 |title=Re: git and bzr |date=2006-11-28}}, on using git-blame to show code moved between source files. (Briefly, given a file in revision ''N'', a file of the same name in revision ''N'' − 1 is its default ancestor. However, when there is no like-named file in revision ''N'' − 1, Git searches for a file that existed only in revision ''N'' − 1 and is very similar to the new file.) However, it does require more [[CPU]]-intensive work every time the history is reviewed, and several options to adjust the heuristics are available. This mechanism does not always work; sometimes a file that is renamed with changes in the same commit is read as a deletion of the old file and the creation of a new file. Developers can work around this limitation by committing the rename and the changes separately. [118] => [119] => Git implements several merging strategies; a non-default strategy can be selected at merge time:{{cite web |last=Torvalds |first=Linus |url=https://www.kernel.org/pub/software/scm/git/docs/git-merge.html |title=git-merge(1) |date=2007-07-18 |url-status=live |archive-url=https://web.archive.org/web/20160716100147/https://www.kernel.org/pub/software/scm/git/docs/git-merge.html |archive-date=16 July 2016}} [120] => * ''resolve'': the traditional [[three-way merge]] algorithm. [121] => * ''recursive'': This is the default when pulling or merging one branch, and is a variant of the three-way merge algorithm. {{quote|When there are more than one common ancestors that can be used for a three-way merge, it creates a merged tree of the common ancestors and uses that as the reference tree for the three-way merge. This has been reported to result in fewer merge conflicts without causing mis-merges by tests done on prior merge commits taken from Linux 2.6 kernel development history. Also, this can detect and handle merges involving renames.|Linus Torvalds{{cite web |last=Torvalds |first=Linus |url=http://revctrl.org/CrissCrossMerge |title=CrissCrossMerge |date=2007-07-18 |url-status=dead |archive-url=https://web.archive.org/web/20060113122252/http://revctrl.org/CrissCrossMerge |archive-date=13 January 2006}}}} [122] => * ''octopus'': This is the default when merging more than two heads. [123] => [124] => ===Data structures=== [125] => Git's primitives are not inherently a [[Version control|source-code management]] system. Torvalds explains:{{cite mailing list |mailing-list=linux-kernel |last=Torvalds |first=Linus |url=https://marc.info/?l=linux-kernel&m=111314792424707 |title=Re: more git updates... |date=2005-04-10}} [126] => {{quote|In many ways you can just see git as a filesystem—it's [[Content-addressable storage|content-addressable]], and it has a notion of versioning, but I really designed it coming at the problem from the viewpoint of a ''filesystem'' person (hey, kernels is what I do), and I actually have absolutely ''zero'' interest in creating a traditional SCM system.}} [127] => [128] => From this initial design approach, Git has developed the full set of features expected of a traditional SCM,{{cite mailing list |mailing-list=git |last=Torvalds |first=Linus |url=https://marc.info/?l=git&m=114314642000462 |title=Re: Errors GITtifying GCC and Binutils |date=2006-03-23 |access-date=3 February 2017 |archive-date=22 March 2021 |archive-url=https://web.archive.org/web/20210322043017/https://marc.info/?l=git&m=114314642000462 |url-status=live }} with features mostly being created as needed, then refined and extended over time. [129] => [130] => [[File:Git operations.svg|thumb|Some data flows and storage levels in the Git revision control system]] [131] => [132] => Git has two [[data structure]]s: a mutable ''index'' (also called ''stage'' or ''cache'') that caches information about the working directory and the next revision to be committed; and an immutable, append-only ''object database''. [133] => [134] => The index serves as a connection point between the object database and the working tree. [135] => [136] => The [[object store]] contains five types of objects:{{cite web |title=Git – Git Objects |url=https://git-scm.com/book/en/v2/Git-Internals-Git-Objects |website=Git}} [137] => * A '''blob''' is the content of a [[computer file|file]]. Blobs have no proper file name, time stamps, or other metadata (a blob's name internally is a hash of its content). In Git, each blob is a version of a file, in which is the file's data.{{sfn | Chacon | Straub | 2014 | pp=81-83}} [138] => * A '''tree''' object is the equivalent of a directory. It contains a list of file names,{{sfn | Chacon | Straub | 2014 | pp=485-488}} each with some type bits and a reference to a blob or tree object that is that file, symbolic link, or directory's contents. These objects are a snapshot of the source tree. (In whole, this comprises a [[Merkle tree]], meaning that only a single hash for the root tree is sufficient and actually used in commits to precisely pinpoint to the exact state of whole tree structures of any number of sub-directories and files.) [139] => * A '''commit''' object links tree objects together into history. It contains the name of a tree object (of the top-level source directory), a timestamp, a log message, and the names of zero or more parent commit objects.{{sfn | Chacon | Straub | 2014 | pp=488-490}} [140] => * A '''tag''' object is a container that contains a reference to another object and can hold added meta-data related to another object. Most commonly, it is used to store a [[digital signature]] of a commit object corresponding to a particular release of the data being tracked by Git.{{sfn | Chacon | Straub | 2014 | pp=495-496}} [141] => * A '''packfile''' object collects various other objects into a [[zlib]]-compressed bundle for compactness and ease of transport over network protocols.{{sfn | Chacon | Straub | 2014 | pp=497-501}} [142] => [143] => Each object is identified by a SHA-1 [[Cryptographic hash function|hash]] of its contents. Git computes the hash and uses this value for the object's name. The object is put into a directory matching the first two characters of its hash. The rest of the hash is used as the file name for that object. [144] => [145] => Git stores each revision of a file as a unique blob. The relationships between the blobs can be found through examining the tree and commit objects. Newly added objects are stored in their entirety using zlib compression. This can consume a large amount of disk space quickly, so objects can be combined into ''packs'', which use [[Delta encoding|delta compression]] to save space, storing blobs as their changes relative to other blobs. [146] => [147] => Additionally, Git stores labels called refs (short for references) to indicate the locations of various commits. They are stored in the reference database and are respectively:{{cite web |title=Git – Git References |url=https://git-scm.com/book/en/v2/Git-Internals-Git-References |website=Git}} [148] => * '''Heads (branches)''': Named references that are advanced automatically to the new commit when a commit is made on top of them. [149] => * '''HEAD''': A reserved head that will be compared against the working tree to create a commit. [150] => * '''Tags''': Like branch references but fixed to a particular commit. Used to label important points in history. [151] => [152] => ===References=== [153] => Every object in the Git database that is not referred to may be cleaned up by using a garbage collection command or automatically. An object may be referenced by another object or an explicit reference. Git knows different types of references. The commands to create, move, and delete references vary. git show-ref lists all references. Some types are: [154] => * ''heads'': refers to an object locally, [155] => * ''remotes'': refers to an object which exists in a remote repository, [156] => * ''stash'': refers to an object not yet committed, [157] => * ''meta'': e.g. a configuration in a bare repository, user rights; the refs/meta/config namespace was introduced retrospectively, gets used by [[Gerrit (software)|Gerrit]],{{cite web | title=Project Configuration File Format | website=Gerrit Code Review | url=https://gerrit-review.googlesource.com/Documentation/config-project-config.html | access-date=2 February 2020 | archive-date=3 December 2020 | archive-url=https://web.archive.org/web/20201203033602/https://gerrit-review.googlesource.com/Documentation/config-project-config.html | url-status=live }} [158] => * ''tags'': see above. [159] => [160] => ==Implementations== [161] => [[File:GNOME gitg.png|thumb|[[GNOME Core Applications|gitg]] is a graphical front-end using [[GTK+]].]] [162] => [163] => Git (the main implementation in C) is primarily developed on [[Linux]], although it also supports most major operating systems, including the BSDs ([[DragonFly BSD]], [[FreeBSD]], [[NetBSD]], and [[OpenBSD]]), [[Solaris (operating system)|Solaris]], [[macOS]], and [[Microsoft Windows|Windows]].{{cite web |url=https://git-scm.com/downloads |access-date=14 May 2012 |title=downloads |url-status=live |archive-url=https://web.archive.org/web/20120508021315/http://git-scm.com/downloads |archive-date=8 May 2012}}{{cite web|access-date=30 November 2021|title=git package versions – Repology|url=https://repology.org/project/git/versions|url-status=dead|archive-date=19 January 2022|archive-url=https://web.archive.org/web/20220119103832/https://repology.org/project/git/versions}} [164] => [165] => The first Windows [[porting|port]] of Git was primarily a Linux-emulation framework that hosts the Linux version. Installing Git under Windows creates a similarly named Program Files directory containing the [[Mingw-w64]] port of the [[GNU Compiler Collection]], [[Perl]] 5, [[MSYS2]] (itself a fork of [[Cygwin]], a Unix-like emulation environment for Windows) and various other Windows ports or emulations of Linux utilities and libraries. Currently, native Windows builds of Git are distributed as 32- and 64-bit installers.{{cite web |url=https://github.com/msysgit/msysgit|access-date=20 September 2016 |title=msysGit |website=[[GitHub]] |url-status=live |archive-url=https://web.archive.org/web/20161010143600/https://github.com/msysgit/msysgit |archive-date=10 October 2016}} The git official website currently maintains a build of Git for Windows, still using the MSYS2 environment.{{cite web |title=Git – Downloading Package |url=https://git-scm.com/download/win |website=Git}} ([https://github.com/git-for-windows/git source code]) [166] => [167] => The JGit implementation of Git is a pure [[Java (software platform)|Java]] software library, designed to be embedded in any Java application. JGit is used in the [[Gerrit (software)|Gerrit]] code-review tool, and in EGit, a Git client for the [[Eclipse (software)|Eclipse]] IDE.{{cite web |url=https://www.eclipse.org/jgit/ |access-date=24 August 2012 |title=JGit |url-status=live |archive-url=https://web.archive.org/web/20120831201256/http://eclipse.org/jgit/ |archive-date=31 August 2012}} [168] => [169] => Go-git is an [[Open-source software|open-source]] implementation of Git written in pure [[Go (programming language)|Go]].{{cite web|url=https://git-scm.com/book/en/v2/Appendix-B%3A-Embedding-Git-in-your-Applications-go-git|title=Git – go-git|website=Git|access-date=2019-04-19}} It is currently used for backing projects as a [[SQL]] interface for Git code repositories{{citation|title=SQL interface to Git repositories, written in Go.|url=https://github.com/src-d/gitbase|website=github.com|access-date=2019-04-19}} and providing [[encryption]] for Git.{{cite web|url=https://keybase.io/blog/encrypted-git-for-everyone|title=Keybase launches encrypted git|website=keybase.io|access-date=2019-04-19}} [170] => [171] => Dulwich is an implementation of Git written in pure [[Python (programming language)|Python]] with support for CPython 3.6 and later and Pypy.{{cite web |url=https://github.com/jelmer/dulwich/tree/8d124dc920a9c529f841888c4229f9bd508c2507?tab=readme-ov-file#supported-versions-of-python |access-date=29 April 2024 |title=Dulwich GitHub Repository README.md |url-status=live |archive-url=https://web.archive.org/web/20240429015034/https://github.com/jelmer/dulwich#supported-versions-of-python |archive-date=29 April 2024}} [172] => [173] => The libgit2 implementation of Git is an ANSI C software library with no other dependencies, which can be built on multiple platforms, including Windows, Linux, macOS, and BSD.{{cite web |url=https://github.com/libgit2/libgit2/blob/main/README.md |access-date=24 August 2012 |title=libgit2 |website=[[GitHub]] |url-status=live |archive-url=https://web.archive.org/web/20160411135623/https://github.com/libgit2/libgit2/blob/master/README.md |archive-date=11 April 2016}} It has bindings for many programming languages, including [[Ruby (programming language)|Ruby]], Python, and [[Haskell (programming language)|Haskell]].{{cite web |url=https://github.com/libgit2/rugged |access-date=24 August 2012 |title=rugged |website=[[GitHub]] |url-status=live |archive-url=https://web.archive.org/web/20130724042431/https://github.com/libgit2/rugged |archive-date=24 July 2013}}{{cite web |url=https://github.com/libgit2/pygit2 |access-date=24 August 2012 |title=pygit2 |website=[[GitHub]] |url-status=live |archive-url=https://web.archive.org/web/20150805001221/https://github.com/libgit2/pygit2 |archive-date=5 August 2015}}{{cite web |url=https://hackage.haskell.org/package/hlibgit2 |access-date=30 April 2013 |title=hlibgit2 |url-status=live |archive-url=https://web.archive.org/web/20130525064750/http://hackage.haskell.org/package/hlibgit2 |archive-date=25 May 2013}} [174] => [175] => JS-Git is a [[JavaScript]] implementation of a subset of Git.{{cite web |url=https://github.com/creationix/js-git |title=js-git: a JavaScript implementation of Git |website=[[GitHub]] |access-date=2013-08-13 |url-status=live |archive-url=https://web.archive.org/web/20130807173550/https://github.com/creationix/js-git |archive-date=7 August 2013}} [176] => [177] => GameOfTrees is an open-source implementation of Git for the OpenBSD project.{{Cite web |title=Game of Trees |url=https://gameoftrees.org/ |access-date=2024-03-10 |website=gameoftrees.org}} [178] => [179] => ==Git server== [180] => [[File:Gitweb.png|thumb|Screenshot of Gitweb interface showing a commit [[diff]] ]] [181] => [182] => As Git is a distributed version control system, it could be used as a server out of the box. It is shipped with a built-in command git daemon which starts a simple TCP server running on the Git protocol.{{sfn | Chacon | Straub | 2014 | pp=138-139}}{{cite web|url=https://git-scm.com/book/en/v2/Git-on-the-Server-Git-Daemon|title=Git – Git Daemon|website=Git|access-date=2019-07-10}} Dedicated Git HTTP servers help (amongst other features) by adding access control, displaying the contents of a Git repository via the web interfaces, and managing multiple repositories. Already existing Git repositories can be cloned and shared to be used by others as a centralized repo. It can also be accessed via remote shell just by having the Git software installed and allowing a user to log in.[https://git-scm.com/book/en/Git-on-the-Server-Setting-Up-the-Server 4.4 Git on the Server – Setting Up the Server] {{webarchive|url=https://web.archive.org/web/20141022015944/http://git-scm.com/book/en/Git-on-the-Server-Setting-Up-the-Server |date=22 October 2014}}, Pro Git. Git servers typically listen on [[Port (computer networking)|TCP port]] 9418.{{cite web |url=https://git-scm.com/book/ch4-1.html#The-Git-Protocol |title=1.4 Getting Started – Installing Git |publisher=Git |access-date=2013-11-01 |url-status=live |archive-url=https://web.archive.org/web/20131102192025/http://git-scm.com/book/ch4-1.html#The-Git-Protocol |archive-date=2 November 2013}} [183] => [184] => ===Open source=== [185] => * Hosting the Git server using the Git Binary.{{cite book|chapter-url=https://git-scm.com/book/en/v2/Git-on-the-Server-Setting-Up-the-Server|chapter=Git on the Server – Setting Up the Server|first1=Scott|last1=Chacon|first2=Ben|last2=Straub|title=Pro Git|publisher=Apress|year=2014|isbn=978-1484200773|edition=2nd}} [186] => * [[Gerrit (software)|Gerrit]], a Git server configurable to support code reviews and provide access via ssh, an integrated [[Apache MINA]] or OpenSSH, or an integrated [[Jetty (webserver)|Jetty]] web server. Gerrit provides integration for LDAP, Active Directory, OpenID, OAuth, Kerberos/GSSAPI, X509 https client certificates. With Gerrit 3.0 all configurations will be stored as Git repositories, and no database is required to run. Gerrit has a pull-request feature implemented in its core but lacks a GUI for it. [187] => * [[Phabricator]], a spin-off from Facebook. As Facebook primarily uses [[Mercurial]], Git support is not as prominent.[https://secure.phabricator.com/book/phabricator/article/diffusion_hosting/ Diffusion User Guide: Repository Hosting] {{Webarchive|url=https://web.archive.org/web/20200920235815/https://secure.phabricator.com/book/phabricator/article/diffusion_hosting/ |date=20 September 2020 }}. [188] => * [[RhodeCode]] Community Edition (CE), supporting Git, [[Mercurial]] and [[Apache Subversion|Subversion]] with an [[AGPLv3|AGPLv3 license]]. [189] => * [[Kallithea (software)|Kallithea]], supporting both Git and [[Mercurial]], developed in [[Python (programming language)|Python]] with [[GPL license]]. [190] => * External projects like gitolite,{{cite web|url=https://gitolite.com/gitolite/index.html|title=Gitolite: Hosting Git Repositories}} which provide scripts on top of Git software to provide fine-grained access control. [191] => * There are several other FLOSS solutions for self-hosting, including Gogs{{cite web|url=https://gogs.io/ |title=Gogs: A painless self-hosted Git service}} and [[Gitea]], a fork of Gogs, both developed in [[Go (programming language)|Go language]] with [[MIT license]]. [192] => [193] => ===Git server as a service=== [194] => {{See also|Comparison of source-code-hosting facilities}} [195] => [196] => There are many offerings of Git repositories as a service. The most popular are [[GitHub]], [[SourceForge]], [[Bitbucket]] and [[GitLab]].{{Cite web|date=2020-03-22|title=Highlights from Git 2.26|url=https://github.blog/2020-03-22-highlights-from-git-2-26/|access-date=2020-11-25|website=The GitHub Blog|language=en-US|quote=You may remember when Git introduced a new version of its network fetch protocol way back in 2018. That protocol is now used by default in 2.26, so let’s refresh ourselves on what that means. The biggest problem with the old protocol is that the server would immediately list all of the branches, tags, and other references in the repository before the client had a chance to send anything. For some repositories, this could mean sending megabytes of extra data, when the client really only wanted to know about the master branch. The new protocol starts with the client request and provides a way for the client to tell the server which references it’s interested in. Fetching a single branch will only ask about that branch, while most clones will only ask about branches and tags. This might seem like everything, but server repositories may store other references (such as the head of every pull request opened in the repository since its creation). Now, fetches from large repositories improve in speed, especially when the fetch itself is small, which makes the cost of the initial reference advertisement more expensive relatively speaking. And the best part is that you won’t need to do anything! Due to some clever design, any client that speaks the new protocol can work seamlessly with both old and new servers, falling back to the original protocol if the server doesn’t support it. The only reason for the delay between introducing the protocol and making it the default was to let early adopters discover any bugs.|archive-date=22 March 2021|archive-url=https://web.archive.org/web/20210322043004/https://github.blog/2020-03-22-highlights-from-git-2-26/|url-status=live}}{{cite web | title=github.com Competitive Analysis, Marketing Mix and Traffic | website=Alexa | url=https://www.alexa.com/siteinfo/github.com | access-date=2 February 2020 | archive-date=31 March 2013 | archive-url=https://web.archive.org/web/20130331175229/http://www.alexa.com/siteinfo/github.com | url-status=dead }}{{cite web | title=sourceforge.net Competitive Analysis, Marketing Mix and Traffic | website=Alexa | url=https://www.alexa.com/siteinfo/sourceforge.net | access-date=2 February 2020 | archive-date=20 October 2020 | archive-url=https://web.archive.org/web/20201020111244/https://www.alexa.com/siteinfo/sourceforge.net | url-status=live }}{{cite web | title=bitbucket.org Competitive Analysis, Marketing Mix and Traffic | website=Alexa | url=https://www.alexa.com/siteinfo/bitbucket.org | access-date=2 February 2020 | archive-date=23 June 2017 | archive-url=https://web.archive.org/web/20170623162208/http://www.alexa.com/siteinfo/bitbucket.org | url-status=dead }}{{cite web | title=gitlab.com Competitive Analysis, Marketing Mix and Traffic | website=Alexa | url=https://www.alexa.com/siteinfo/gitlab.com | access-date=2 February 2020 | archive-date=30 November 2017 | archive-url=https://web.archive.org/web/20171130123149/https://www.alexa.com/siteinfo/gitlab.com | url-status=live }} [197] => [198] => ==Adoption== [199] => The [[Eclipse Foundation]] reported in its annual community survey that as of May 2014, Git is now the most widely used source-code management tool, with 42.9% of professional software developers reporting that they use Git as their primary source-control system{{cite web |url=https://ianskerrett.wordpress.com/2014/06/23/eclipse-community-survey-2014-results/ |title=Eclipse Community Survey 2014 results | Ian Skerrett |publisher=Ianskerrett.wordpress.com |date=2014-06-23 |access-date=2014-06-23 |url-status=live |archive-url=https://web.archive.org/web/20140625152145/http://ianskerrett.wordpress.com/2014/06/23/eclipse-community-survey-2014-results/ |archive-date=25 June 2014}} compared with 36.3% in 2013, 32% in 2012; or for Git responses excluding use of [[GitHub]]: 33.3% in 2014, 30.3% in 2013, 27.6% in 2012 and 12.8% in 2011.{{cite web |url=https://eclipse.org/org/community_survey/Survey_Final_Results_2012.xls |title=Results of Eclipse Community Survey 2012 |publisher=eclipse.org|url-status=live |archive-url=https://web.archive.org/web/20160411135719/http://www.eclipse.org/org/community_survey/Survey_Final_Results_2012.xls |archive-date=11 April 2016}} Open-source directory [[Black Duck Open Hub]] reports a similar uptake among open-source projects.{{cite web |url=https://www.openhub.net/repositories/compare |title=Compare Repositories – Open Hub |url-status=live |archive-url=https://web.archive.org/web/20140907051024/https://www.openhub.net/repositories/compare |archive-date=7 September 2014}} [200] => [201] => [[Stack Overflow]] has included [[version control]] in their annual developer survey{{cite web | url=https://insights.stackoverflow.com/survey | title=Stack Overflow Annual Developer Survey | publisher=Stack Exchange, Inc. | access-date=9 January 2020 | quote=Stack Overflow’s annual Developer Survey is the largest and most comprehensive survey of people who code around the world. Each year, we field a survey covering everything from developers' favorite technologies to their job preferences. This year marks the ninth year we’ve published our annual Developer Survey results, and nearly 90,000 developers took the 20-minute survey earlier this year.}} in 2015 (16,694 responses),{{cite web |title=Stack Overflow Developer Survey 2015 |url=https://insights.stackoverflow.com/survey/2015#tech-sourcecontrol |publisher=Stack Overflow |access-date=29 May 2019 |url-status=dead |archive-url=https://web.archive.org/web/20190504144447/https://insights.stackoverflow.com/survey/2015#tech-sourcecontrol |archive-date=4 May 2019}} 2017 (30,730 responses),{{cite web |title=Stack Overflow Developer Survey 2017 |url=https://insights.stackoverflow.com/survey/2017#work-_-version-control |publisher=Stack Overflow |access-date=29 May 2019 |url-status=dead |archive-url=https://web.archive.org/web/20190529004901/https://insights.stackoverflow.com/survey/2017#work-_-version-control |archive-date=29 May 2019}} 2018 (74,298 responses){{cite web |title=Stack Overflow Developer Survey 2018 |url=https://insights.stackoverflow.com/survey/2018#work-_-version-control |publisher=Stack Overflow |access-date=29 May 2019 |url-status=dead |archive-url=https://web.archive.org/web/20190530142357/https://insights.stackoverflow.com/survey/2018/#work-_-version-control |archive-date=30 May 2019}} and 2022 (71,379 responses).{{Cite web |title=Stack Overflow Developer Survey 2022 |url=https://survey.stackoverflow.co/2022/#section-version-control-version-control-systems |access-date=2022-08-04 |website=Stack Overflow |language=en}} Git was the overwhelming favorite of responding developers in these surveys, reporting as high as 93.9% in 2022. [202] => [203] => Version control systems used by responding developers: [204] => {| class="wikitable sortable" [205] => |- [206] => ! Name !! 2015 !! 2017 !! 2018 [207] => !2022 [208] => |- [209] => | Git || 69.3% || 69.2% || 87.2% [210] => |93.9% [211] => |- [212] => | [[Apache Subversion|Subversion]] || 36.9% || 9.1% || 16.1% [213] => |5.2% [214] => |- [215] => | [[Team Foundation Version Control|TFVC]] || 12.2% || 7.3% || 10.9% [216] => |{{efn-lr|name=fn0}} [217] => |- [218] => | [[Mercurial]] || 7.9% || 1.9% || 3.6% [219] => |1.1% [220] => |- [221] => | [[Concurrent Versions System|CVS]] || 4.2% || {{efn-lr|name=fn0|Not listed as an option in this survey}} || {{efn-lr|name=fn0}} [222] => |{{efn-lr|name=fn0}} [223] => |- [224] => | [[Perforce Helix|Perforce]] || 3.3% || {{efn-lr|name=fn0}} || {{efn-lr|name=fn0}} [225] => |{{efn-lr|name=fn0}} [226] => |- [227] => | [[Visual SourceSafe|VSS]] || {{efn-lr|name=fn0}} || 0.6% || {{efn-lr|name=fn0}} [228] => |{{efn-lr|name=fn0}} [229] => |- [230] => | [[IBM DevOps Code ClearCase]] || {{efn-lr|name=fn0}} || 0.4% || {{efn-lr|name=fn0}} [231] => |{{efn-lr|name=fn0}} [232] => |- [233] => | Zip file backups || {{efn-lr|name=fn0}} || 2.0% || 7.9% [234] => |{{efn-lr|name=fn0}} [235] => |- [236] => | Raw network sharing || {{efn-lr|name=fn0}} || 1.7% || 7.9% [237] => |{{efn-lr|name=fn0}} [238] => |- [239] => | Other || 5.8% || 3.0% || {{efn-lr|name=fn0}} [240] => |{{efn-lr|name=fn0}} [241] => |- [242] => | None || 9.3% || 4.8% || 4.8% [243] => |4.3% [244] => |} [245] => [246] => The UK IT jobs website itjobswatch.co.uk reports that as of late September 2016, 29.27% of UK permanent software development job openings have cited Git,{{cite web |url=https://www.itjobswatch.co.uk/jobs/uk/git%20%28software%29.do |title=Git (software) Jobs, Average Salary for Git Distributed Version Control System Skills |publisher=Itjobswatch.co.uk |access-date=2016-09-30 |url-status=live |archive-url=https://web.archive.org/web/20161008072321/http://www.itjobswatch.co.uk/jobs/uk/git%20(software).do |archive-date=8 October 2016}} ahead of 12.17% for Microsoft [[Team Foundation Server]],{{cite web |url=https://www.itjobswatch.co.uk/jobs/uk/team%20foundation%20server.do |title=Team Foundation Server Jobs, Average Salary for Microsoft Team Foundation Server (TFS) Skills |publisher=Itjobswatch.co.uk |access-date=2016-09-30 |url-status=live |archive-url=https://web.archive.org/web/20161029185314/http://www.itjobswatch.co.uk/jobs/uk/team%20foundation%20server.do |archive-date=29 October 2016}} 10.60% for [[Apache Subversion|Subversion]],{{cite web |url=https://www.itjobswatch.co.uk/jobs/uk/subversion.do |title=Subversion Jobs, Average Salary for Apache Subversion (SVN) Skills |publisher=Itjobswatch.co.uk |access-date=2016-09-30 |url-status=live |archive-url=https://web.archive.org/web/20161025011418/http://www.itjobswatch.co.uk/jobs/uk/subversion.do |archive-date=25 October 2016}} 1.30% for [[Mercurial]],{{cite web |url=https://www.itjobswatch.co.uk/jobs/uk/mercurial.do |title=Mercurial Jobs, Average Salary for Mercurial Skills |publisher=Itjobswatch.co.uk |access-date=2016-09-30 |url-status=live |archive-url=https://web.archive.org/web/20160923081538/http://www.itjobswatch.co.uk/jobs/uk/mercurial.do |archive-date=23 September 2016}} and 0.48% for [[Visual SourceSafe]].{{cite web |url=https://www.itjobswatch.co.uk/jobs/uk/vss/sourcesafe.do |title=VSS/SourceSafe Jobs, Average Salary for Microsoft Visual SourceSafe (VSS) Skills |publisher=Itjobswatch.co.uk |access-date=2016-09-30 |url-status=live |archive-url=https://web.archive.org/web/20161029043610/http://www.itjobswatch.co.uk/jobs/uk/vss/sourcesafe.do |archive-date=29 October 2016}} [247] => [248] => ===Extensions=== [249] => There are many ''Git extensions'', like [https://github.com/git-lfs/git-lfs Git LFS], which started as an extension to Git in the GitHub community and is now widely used by other repositories. Extensions are usually independently developed and maintained by different people, but at some point in the future, a widely used extension can be merged with Git. [250] => [251] => Other open-source Git extensions include: [252] => [253] => * [[git-annex]], a distributed file synchronization system based on Git [254] => * [[git-flow]], a set of Git extensions to provide high-level repository operations for [https://nvie.com/posts/a-successful-git-branching-model/ Vincent Driessen's branching model] [255] => * [https://github.com/VirtusLab/git-machete git-machete], a repository organizer & tool for automating rebase/merge/pull/push operations [256] => [257] => Microsoft developed the [[Virtual File System for Git]] (VFS for Git; formerly Git Virtual File System or GVFS) extension to handle the size of the [[Microsoft Windows|Windows]] source-code tree as part of their 2017 migration from [[Perforce]]. VFS for Git allows cloned repositories to use placeholders whose contents are downloaded only once a file is accessed.{{cite web |title=Windows switch to Git almost complete: 8,500 commits and 1,760 builds each day |url=https://arstechnica.com/information-technology/2017/05/90-of-windows-devs-now-using-git-creating-1760-windows-builds-per-day/ |website=Ars Technica |date=24 May 2017 |access-date=24 May 2017 |url-status=live |archive-url=https://web.archive.org/web/20170524171707/https://arstechnica.com/information-technology/2017/05/90-of-windows-devs-now-using-git-creating-1760-windows-builds-per-day/ |archive-date=24 May 2017}} [258] => [259] => ==Conventions== [260] => Git does not impose many restrictions on how it should be used, but some conventions are adopted in order to organize histories, especially those which require the cooperation of many contributors. [261] => [262] => * The ''master'' branch is created by default with ''git init'' {{sfn | Chacon | Straub | 2014 | pp=81-83}}{{cite web|url=https://git-scm.com/docs/git-init|title=git-init|work=Git|archive-url=https://web.archive.org/web/20220315095632/https://git-scm.com/docs/git-init|archive-date=March 15, 2022|url-status=live}} and is often used as the branch that other changes are merged into.{{cite web |title=Git – Branches in a Nutshell |url=https://git-scm.com/book/en/v2/Git-Branching-Branches-in-a-Nutshell#ch03-git-branching |website=Git |access-date=15 June 2020 |quote=The "master" branch in Git is not a special branch. It is exactly like any other branch. The only reason nearly every repository has one is that the git init command creates it by default and most people don’t bother to change it. |archive-date=20 December 2020 |archive-url=https://web.archive.org/web/20201220123258/http://git-scm.com/book/en/v2/Git-Branching-Branches-in-a-Nutshell#ch03-git-branching |url-status=live }} Correspondingly, the default name of the upstream remote is ''origin''{{sfn | Chacon | Straub | 2014 | pp=103-109}} and so the name of the default remote branch is ''origin/master''. The use of ''master'' as the default branch name is not universally true; repositories created in GitHub and GitLab initialize with a ''main'' branch instead of ''master'',{{Citation|title=github/renaming|date=2020-12-04|url=https://github.com/github/renaming|publisher=GitHub|access-date=2020-12-04}}{{Citation|title=Default branch name for new repositories now main|date=2021-06-22|url=https://about.gitlab.com/releases/2021/06/22/gitlab-14-0-released/#default-branch-name-for-new-repositories-now-main|publisher=GitLab|access-date=2021-06-22}} though the default can be changed by the user. [263] => * Pushed commits should usually not be overwritten, but should rather be ''revert''ed{{cite web |title=Git Revert {{!}} Atlassian Git Tutorial |url=https://www.atlassian.com/git/tutorials/undoing-changes/git-revert |website=Atlassian |language=en |quote=Reverting has two important advantages over resetting. First, it doesn’t change the project history, which makes it a "safe" operation for commits that have already been published to a shared repository.}} (a commit is made on top which reverses the changes to an earlier commit). This prevents shared new commits based on shared commits from being invalid because the commit on which they are based does not exist in the remote. If the commits contain sensitive information, they should be removed, which involves a more complex procedure to rewrite history. [264] => * The ''git-flow''{{cite web |title=Gitflow Workflow {{!}} Atlassian Git Tutorial |url=https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow |website=Atlassian |access-date=15 June 2020 |language=en}} workflow and naming conventions are often adopted to distinguish feature specific unstable histories (feature/*), unstable shared histories (develop), production ready histories (main), and emergency patches to released products (hotfix). [265] => *''Pull requests'' are not a feature of git, but are commonly provided by git cloud services. A pull request is a request by one user to merge a branch of their repository fork into another repository sharing the same history (called the ''upstream'' remote).{{sfn | Chacon | Straub | 2014 | pp=170-174}}{{cite web |title=Forking Workflow {{!}} Atlassian Git Tutorial |url=https://www.atlassian.com/git/tutorials/comparing-workflows/forking-workflow |website=Atlassian |access-date=15 June 2020 |language=en}} The underlying function of a pull request is no different than that of an administrator of a repository pulling changes from another remote (the repository that is the source of the pull request). However, the pull request itself is a ticket managed by the hosting server which initiates scripts to perform these actions; it is not a feature of git SCM. [266] => [267] => ==Security== [268] => Git does not provide access-control mechanisms, but was designed for operation with other tools that specialize in access control.{{cite web |url=https://wincent.com/wiki/git_repository_access_control |title=Git repository access control |access-date=2016-09-06 |url-status=live |archive-url=https://web.archive.org/web/20160914114143/https://wincent.com/wiki/git_repository_access_control |archive-date=14 September 2016}} [269] => [270] => On 17 December 2014, an exploit was found affecting the [[Windows]] and [[macOS]] versions of the Git client. An attacker could perform [[arbitrary code execution]] on a target computer with Git installed by creating a malicious Git tree (directory) named ''.git'' (a directory in Git repositories that stores all the data of the repository) in a different case (such as .GIT or .Git, needed because Git does not allow the all-lowercase version of ''.git'' to be created manually) with malicious files in the ''.git/hooks'' subdirectory (a folder with executable files that Git runs) on a repository that the attacker made or on a repository that the attacker can modify. If a Windows or Mac user ''pulls'' (downloads) a version of the repository with the malicious directory, then switches to that directory, the .git directory will be overwritten (due to the case-insensitive trait of the Windows and Mac filesystems) and the malicious executable files in ''.git/hooks'' may be run, which results in the attacker's commands being executed. An attacker could also modify the ''.git/config'' configuration file, which allows the attacker to create malicious Git aliases (aliases for Git commands or external commands) or modify extant aliases to execute malicious commands when run. The vulnerability was patched in version 2.2.1 of Git, released on 17 December 2014, and announced the next day.{{cite web |url= https://developer.atlassian.com/blog/2014/12/securing-your-git-server/ |title= Securing your Git server against CVE-2014-9390 |date= 20 December 2014 |access-date= 22 December 2014 |last= Pettersen |first= Tim |url-status= live |archive-url= https://web.archive.org/web/20141224012942/https://developer.atlassian.com/blog/2014/12/securing-your-git-server/ |archive-date= 24 December 2014}}{{cite newsgroup |title=[Announce] Git v2.2.1 (and updates to older maintenance tracks) |author= Hamano, J. C.|date= 18 December 2014|newsgroup=gmane.linux.kernel |url=https://article.gmane.org/gmane.linux.kernel/1853266 |archive-url=https://web.archive.org/web/20141219024646/http://article.gmane.org/gmane.linux.kernel/1853266 |url-status=dead |archive-date=19 December 2014 |access-date=22 December 2014}} [271] => [272] => Git version 2.6.1, released on 29 September 2015, contained a patch for a security vulnerability ({{CVE|2015-7545}}){{cite web |url=https://people.canonical.com/~ubuntu-security/cve/2015/CVE-2015-7545.html |title=CVE-2015-7545 |date=15 December 2015 |access-date=26 December 2015 |url-status=live |archive-url=https://web.archive.org/web/20151226232616/http://people.canonical.com/~ubuntu-security/cve/2015/CVE-2015-7545.html |archive-date=26 December 2015}} that allowed arbitrary code execution.{{cite web |url=https://github.com/git/git/commit/22f698cb188243b313e024d618283e0293e37140 |title=Git 2.6.1 |website=[[GitHub]] |access-date=26 December 2015 |date=29 September 2015 |url-status=live |archive-url=https://web.archive.org/web/20160411135802/https://github.com/git/git/commit/22f698cb188243b313e024d618283e0293e37140 |archive-date=11 April 2016}} The vulnerability was exploitable if an attacker could convince a victim to clone a specific URL, as the arbitrary commands were embedded in the URL itself.{{cite web |url=http://seclists.org/oss-sec/2015/q4/67 |title=Re: CVE Request: git |author=Blake Burkhart |access-date=26 December 2015 |date=5 October 2015 |display-authors=etal |url-status=live |archive-url=https://web.archive.org/web/20151227054727/http://seclists.org/oss-sec/2015/q4/67 |archive-date=27 December 2015}} An attacker could use the exploit via a [[man-in-the-middle attack]] if the connection was unencrypted, as they could redirect the user to a URL of their choice. Recursive clones were also vulnerable since they allowed the controller of a repository to specify arbitrary URLs via the gitmodules file. [273] => [274] => Git uses [[SHA-1]] hashes internally. Linus Torvalds has responded that the hash was mostly to guard against accidental corruption, and the security a [[Cryptographic hash function|cryptographically secure hash]] gives was just an accidental side effect, with the main security being [[Digital signature|signing]] elsewhere.{{cite web |url=https://security.stackexchange.com/questions/67920/how-safe-are-signed-git-tags-only-as-safe-as-sha-1-or-somehow-safer |title=hash – How safe are signed git tags? Only as safe as SHA-1 or somehow safer? |publisher=Information Security Stack Exchange |date=22 September 2014 |url-status=live |archive-url=https://web.archive.org/web/20160624232415/https://security.stackexchange.com/questions/67920/how-safe-are-signed-git-tags-only-as-safe-as-sha-1-or-somehow-safer |archive-date=24 June 2016}}{{cite web |url=https://stackoverflow.com/questions/28792784/why-does-git-use-a-cryptographic-hash-function |title=Why does Git use a cryptographic hash function? |publisher=Stack Overflow |date=1 March 2015 |url-status=live |archive-url=https://web.archive.org/web/20160701214638/http://stackoverflow.com/questions/28792784/why-does-git-use-a-cryptographic-hash-function |archive-date=1 July 2016}} Since a demonstration of the [[SHAttered]] attack against git in 2017, git was modified to use a SHA-1 variant resistant to this attack. A plan for hash function transition is being written since February 2020.{{cite web |title=Git – hash-function-transition Documentation |url=https://git-scm.com/docs/hash-function-transition/ |website=Git}} [275] => [276] => ==Trademark== [277] => "Git" is a registered word [[trademark]] of [[Software Freedom Conservancy]] under [https://www.tmdn.org/tmview/#/tmview/detail/US500000085961336 US500000085961336] since 2015-02-03. [278] => [279] => ==See also== [280] => {{Portal|Free and open-source software|Linux|Internet}} [281] => * [[Comparison of source-code-hosting facilities]] [282] => * [[Comparison of version-control software]] [283] => * [[List of version-control software]] [284] => [285] => ==Notes== [286] => {{Notelist-lr}} [287] => [288] => ==Citations== [289] => {{Reflist|30em}} [290] => [291] => ==External links== [292] => {{Commons category|Git}} [293] => {{Wikibooks|Git}} [294] => * {{Official website}} [295] => * {{openhub|git|Git}} [296] => [297] => {{Revision control software}} [298] => {{Authority control}} [299] => [300] => [[Category:Git (software)| ]] [301] => [[Category:2005 software]] [302] => [[Category:Concurrent Versions System| ]] [303] => [[Category:Distributed version control systems]] [304] => [[Category:Free version control software]] [305] => [[Category:Free software programmed in C]] [306] => [[Category:Free software programmed in Perl]] [307] => [[Category:Linus Torvalds]] [308] => [[Category:Self-hosting software]] [309] => [[Category:Software using the GPL license]] [310] => [[Category:Software that uses Tk (software)]] [311] => [[Category:Version control systems]] [] => )
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Git

Git is a distributed version control system (VCS) that allows multiple users to collaborate on a project, tracking and managing changes to files. It was created by Linus Torvalds in 2005 to facilitate the development of the Linux kernel, and has since become widely adopted in the software development industry.

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It was created by Linus Torvalds in 2005 to facilitate the development of the Linux kernel, and has since become widely adopted in the software development industry. Git allows users to create their own local repositories, making it easy to work on the same project simultaneously without conflicts. Users can create branches to work on different features or bug fixes, and then merge those changes back into the main branch when they are complete. Git also provides tools for resolving conflicts that may arise during the merging process. One of the key features of Git is its ability to handle distributed development, where multiple users can work on their own copies of a project and then merge their changes together. This makes it ideal for open source projects and for teams spread across different locations. Git stores files and their revision history as snapshots, rather than as a list of changes. This allows for efficient storage and retrieval of data, as well as the ability to easily revert to previous versions of files. Git has a command-line interface, but there are also several graphical user interface (GUI) clients available that provide a more user-friendly experience. Additionally, there are numerous online hosting platforms, such as GitHub and GitLab, that provide a centralized location for hosting and collaborating on Git repositories. Overall, Git revolutionized the way software development is done by providing a flexible and efficient method for managing and tracking changes to code. Its popularity and widespread adoption have made it an essential tool for developers worldwide.

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