I’ve just updated the GitHub README with new instructions for getting UE4 dependencies - there’s no need to manually download and extract zip files for the master or 4.6 preview branch; you can just run the Setup script in a clean repository, and it’ll do everything for you.
As well as downloading the dependencies matching your repository, this will register Git hooks to sync dependencies every time you checkout or merge. It’ll only download the differences needed to update your working tree up to the right state, and it can be safely interrupted or resumed at any point. It won’t clobber changes you make locally without prompting you first. This system works for any commit, not just for the snapshots of ‘latest-preview’ tagged builds that we’ve been limited to until now. If you want to track the master branch in real time, you can! If you want to stick to stable builds verified by our QA team you can track the new promoted branch](https://github.com/EpicGames/UnrealEngine/tree/promoted), which receives merges from master whenever a good build is available.
Of course, this being Epic - the source code for all this is available for you to pore over, and we’ll eagerly take feedback (or pull requests) to improve on it! Some quick pointers - the tool used for downloading is in the repository under Engine/Source/Programs/GitDependencies, and the manifests of files to download are Engine/Build/Commit.gitdeps.xml and Engine/Build/Promoted.gitdeps.xml. Enjoy!
(Note to PS4 and XboxOne developers - you’ll still need to download NDA portions of the Engine from Epic’s FTP site as well as using this system. New zips will be uploaded for every build in the promoted branch.)