GitHub

Github is based around a system of version control called Git. Git is an open-source version control system that was started by Linus Trovalds—the same person who created Linux. Git is similar to other version control systems, such as Subversion, CVS, Mercurial, and Bazaar.

Version control systems keep revisions organized by storing modifications in a central repository, or "repo." This allows developers to collaborate by downloading a new version of the software, making changes, and uploading the newest revision. Developers can see these new changes, download them, and contribute to them. When multiple people collaborate on a project, it's hard to keep track of revisions—who changed what, when, and where those files are stored. GitHub keeps track of all the changes that have been pushed to the repo. No coding is necessary to use Github.

"The concept is based around change: what is the right thing to do, what is the wrong thing?" said Tom Preston-Werner, GitHub's co-founder. "The efficiency of large groups working together is very low in large enterprises. We want to change that."

Git has three core features: forking, pull requests, and merging.

"Forking" is when developers create a new project based off another project that already exists. If a user finds a project on GitHub that they would like to contribute to, they can fork the repo, make the desired changes, and release the revised project as a new repo. If the original repository that was forked to create the new project is updated, those updates can be added to the current fork.This feature encourages the further development of programs and other projects.

A pull request is opened when a user is proposing changes and requesting that someone review and pull in their contribution. Pull requests show differences in the content from both branches, and the user can collaborate and ask for feedback from other users regarding the project.Once the pull request is complete, the changes can then be merged with the initial project.

Besides its public-facing, open-source repositories, GitHub also sells private repositories and on-premise instances of its software for enterprises. This is GitHub's money making feature. Companies pay to use GitHub primarily for its collaboration features. It has become a popular way for people to do all kinds of software work; in 2012 its number of users jumped to 2.8 million from 1.2 million. The number of repositories increased to 4.6 million from 1.7 million the prior year. Solutions for private repositories do not utilize GitHub's network effect, but they are able to use the collaboration features.

GitHub has no managers among its 140 employees. "Everyone has management interests," said cofounder Preston-Werner. "People can work on things that are interesting to them. Companies should exist to optimize happiness, not money. Profits follow."

GitHub's popularity has also made it an important way for companies to recruit engineers, who can show their work or collaborate on the work of others, inside some of the public pull requests. Software engineers routinely include links to their GitHub projects on their resumés, and companies scout for job candidates on GitHub.

In June of 2018, Microsoft acquired GitHub. This is Microsoft CEO Satya Nadella's second big acquisition, following the $26.2 billion acquisition of LinkedIn two years prior. GitHub was valued at $2 billion in 2015, and Microsoft payed $7.5 billion in stock for the company.

At the time of acquisition, executives from both companies insisted that GitHub would remain technologically neutral, welcoming developers to use any code or any cloud service, rather than a Microsoft-walled garden.