Ace3 is a comprehensive framework for WoW AddOn development to streamline many of the common tasks in developing addons. This includes lifecycles, saved variables, configuration, event handling, network communications, and more.
A basic introduction to usage can be found here:
https://www.wowace.com/projects/ace3/pages/getting-started
Documentation can be found here:
https://www.wowace.com/addons/ace3/pages/
A development repository is available on GitHub:
https://github.com/WoWUIDev/Ace3
Please note that the CurseForge/WoWAce SVN repository remains the primary authority, and what should be used in .pkgmeta to reference Ace3.
.pkgmeta reference:
Base Path: https://repos.wowace.com/wow/ace3/trunk
Example for AceAddon-3.0: https://repos.wowace.com/wow/ace3/trunk/AceAddon-3.0
It is recommended to reference the specific Ace3 libraries you are using directly, instead of pulling in the entire package.