OSTree and TreeHub
OSTree is an open-source tool that combines a "git-like" model for committing and downloading bootable filesystem trees, along with a layer for deploying them and managing the bootloader configuration. It is actively developed and support by Red Hat, and used in flatpak and Project Atomic.
For more on why OSTree is the best tool for the job of doing embedded device updates, you can also jump straight to Comparing full-filesystem update strategies.
Since OSTree is "git-like", you can probably imagine that you can have remote repositories. TreeHub is exactly that. It’s seamlessly integrated into the meta-updater layer and into the HERE OTA Connect site itself. Your builds get automatically pushed to TreeHub as soon as you make them, and you can use OTA Connect to wirelessly update your devices—one at a time, or in targeted campaigns. You can even set certain devices to automatically pull updates from TreeHub as soon as they’re pushed, and stop wasting time re-flashing the units on your test bench every time you build new code.