Function remaps 

pub fn remaps(
    workspace: &Path,
    target: &Path,
    name: &str,
    outside: &[(PathBuf, String)],
) -> Vec<(PathBuf, String)>

The folders a release build is remapped from: the workspace’s root (to the package’s name), each package of outside (a folder outside the workspace that the build reads by a path, to its name), CARGO_HOME (/cargo), RUSTUP_HOME (/rustup) and the target folder (/target), in that order. rustc tries the last first, so a folder inside another one still gets its own name.