Adding overrides

How does it work?

Like said in the file formats page, MCInstance files are basically renamed zip files.

Whenever the game starts, the first thing the mod is gonna do (after having checked for updates and such) will be to extract the pack.mcinstance file in a temporary folder. Then, it will download every resources and selected optional resources into the overrides folder. Finally the mod will try to merge the overrides folder with the .minecraft root folder.

And then, if there was no errors beforehand, the mod will simply disable the pack.mcinstance file (it will either add .disabled to its name or delete it entirely, depending on the config) so you can launch the game back afterwards.

How to use the overrides feature?

If you understood the previous point correctly, you'll easily understand that you can include any file in the overrides folder. Simply place your files inside it like you would in a standard .minecraft folder. Then, just add the overrides folder to your MCInstance archive.

NOTE 1: Previous versions of the mod allowed to clear entire folders. This might return in the future but in a different way, for now just consider that it only merges stuff.

NOTE 2: It is possible to overwrite existing mod files, even if they're already loaded by Forge. This works as expected, however, keep in mind that if you're replacing a loaded jar with one with different classes, the game will probably crash if the mod tries to access the old ones, i can't do much about it.

Thus, it is recommended for users to delete their mods and resourcepacks before doing any modpack update. Users can still add their own mods by using the carryover folder anyways.

Sided overrides

Since version 2.5, a sided overrides feature was added. Basically, you can now use a client-overrides or a server-overrides folder to include files only used either on the client or the server side. The normal overrides folder should be used for general files that apply both to the client and the server sides.

Those work exactly like the normal overrides folder, just add your files like you would in the .minecraft folder. Those folders will get merged right after the general overrides.

NOTE: Currently, those files overwrite downloaded files with the same name. I'm not sure this behavior will stay the same.