Replacing everything

Copy the whole lua/uji folder of the uji source into ~/.config/uji/lua/uji. Every module then comes from your copy. A file you delete from your copy falls back to the built-in one.

To run a complete tree kept somewhere else, set UJI_RUNTIME to the directory that contains its uji folder. uji then uses none of its built-in files, and replacements in your config and packs still apply on top.

Such a tree needs one module. uji.boot returns the function that uji runs with the command line as the first task. uji stops when no task is left, or after uji.os.exit or uji.os.restart. The modules built into uji stay available to the tree, such as require("uji.sys.fs"), and Native modules describes how to replace them.