What are some alternatives?
Adobe RoboHelp - Adobe RoboHelp empowers organizations to deliver engaging help and policy content across mobile devices, formats, and platforms.
Atlassian Bitbucket Server - Atlassian Bitbucket Server is a scalable collaborative Git solution.
MadCap Flare - Documentation for Any Audience, Language or Format
Visual Studio Team Services - Visual Studio Team Services (VSTS) provides unlimited Git hosting, cloud build for CI, agile planning and continuous delivery.
Dr.Explain - Dr.Explain software is a help file authoring tool.
GitHub Desktop - GitHub Desktop is a seamless way to contribute to projects on GitHub and GitHub Enterprise.