https://github.com/EpicGames/UnrealEngine#branches
Individual teams have their own development branches for day to day work (dev-core, dev-mobile and dev-sequencer, for example). These branches reflect the cutting edge of the engine and may be buggy - they may not even compile. Battle-hardened developers eager to test new features or work lock-step with us should head to one of these. We aim to merge development branches to master every 3-4 weeks.