Git Annex[1]
Very robust and well-written (Haskell), and extremely fast. An extension (daemon, client, and webui) to git. Gitlab uses this to provide large file support (which is similar to Github's LFS)[2]. Author is a Debian maintainer (and obviously a Haskell dev).
Sync Thing[3]
Fast and professional golang synchronizer with its own protocol[4]. Usually compared to BTsync.
1. https://git-annex.branchable.com/videos/
2. https://about.gitlab.com/2015/02/17/gitlab-annex-solves-the-...