Looks like this originates from
https://github.com/istankovic/cargo-book/commit/
418611304daac22e3590aee9322355ae159802fe
But it's even visible in the render docs:
https://doc.rust-lang.org/cargo/reference/manifest.html#package-selection
:-O
if it is a package, or every member manifest (as if `--all` were specified
on the command-line) for virtual workspaces.
-#TODO: move this to a more appropriate place
### The project layout
If your project is an executable, name the main source file `src/main.rs`. If it