Una's Simple Updater
unsup is a somewhat minimal implementation of a generic working directory syncer in Java. It supports running as a Java agent, to piggy-back off of the launch of another program.
It's designed for syncing Minecraft modpacks, but its design is intentionally generic and nothing ties it to Minecraft. unsup's GUI only shows up when there is something to ask the user (no dialogs flashing up during launch for no reason when everything is up to date)
An unsup.ini must be placed in the working directory for unsup to know what to do.
The updater works hard to ensure the working directory is never left in an inconsistent state. Short of a sudden power loss in the middle of applying changes (an incredibly short time window), an unsup update cannot result in an inconsistent or corrupted working directory.
It does consistency validation on all downloads and on files before overwriting them, warning the user if they've changed something that has been updated. It additionally supports signing manifests using OpenBSD Signify for additional security.
unsup's unique simplified design means it is compatible with all launchers,
from the vanilla launcher to MultiMC. Just add -javaagent:unsup.jar to the
JVM arguments, and place unsup.jar and unsup.ini in the .minecraft
directory.
In Prism Launcher, you can utilize unsup as a "component" by importing this JSON file. This will allow Prism Launcher to download and manage unsup. MultiMC does not support Java agent components.
It also has a built-in concept of environments and flavors, allowing it to be used to manage server installs rather than just clients, and allowing users to pick between multiple mutually incompatible mod sets.
You can either point unsup at a Packwiz pack.toml (recommended), or write a native unsup manifest by hand. See the wiki for info on the native manifest format. The Creator GUI is on hold, as Packwiz has become a de-facto standard for Minecraft modpacks.
unsup has been used for modpacks on versions from 1.4.7 to 1.20.2, both client and server, and is known to work with Forge (both legacy and modern), Fabric, Quilt, and NeoForge. It has successfully powered many modpacks, from small to large. Native manifest and Packwiz manifest support are both quite stable, and have been used extensively.
Signing support is still somewhat experimental, and has not been deployed by anyone at large scale. That someone could be you — please let me know if it works well!
unsup has a minimal and elegant GUI that works everywhere (yes, including macOS) and can have all of its colors customized to make it fit in with your branding. It ships with a dark theme with teal accents.
The unsup agent is released under the LGPLv3. The unsup creator is released under the GPLv3.