jade: I rewrote this PR to be consistent between nix-instantiate and nix eval. It turns out that nix eval *doesn't* copy to store with `--json`, whereas nix-instantiate does. Wat. Closes: https://github.com/lix-project/lix/pull/17 Co-authored-by: tyberiusprime <tyberiusprime@noreply.git.lix.systems> Change-Id: Id22deec1cee0fed3bd5689567869b70bab26bae5