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Phabricator is an open source LAMP (Linux, Apache, MySQL, PHP) application that helps software companies build better software.
There is also a paid hosted version available.
Read Phabricator-Discuss. Plan. Code. Review.
SpecsUpdate
Pros
Pro Designed by software engineers for software engineers
The engineering workflow is far superior to Github style branching and merging. Phabricator separates local representations of the repository from remote, which enables a variety of workflow optimisations, like stacked diffs on a single branch.
Cons
Con Difficult to configure
Compared to a solution like Bitbucket Server (granted Phabricator offers more options), it is difficult to configure. Settings are scattered everywhere and you must drill down through several screens to find some of them. Documentation is very complete but also not always in parity with the application itself.
Recommendations
Comments
Flagged Pros + Cons
Con No editing directly in browser
You must configure an external editor.