What happens under the hood when I install the hooks?

What pre-commit install --install-hooks does:

• clone lorenzwalthert/precommit into its cache and give it a name starting with repo.... On macOS, that repo... lives in ~/.cache/pre-commit/.
• Then, it places an installation script in that repo.
• Then, it runs that script with the working directory being where the script is located, roughly it runs renv::restore().
• As part of running the installation script, it also writes an activation script, that will be executed from your project's working directly, which roughly is 1) change working directory to repo..., 2) renv::load() (which is similar to renv::activate()) and 3) change back to your projects working directory.

When you then run a hook, it sets that activate script as your .Rprofile through an environment variable and executes the hook scripts.