I added a --bye flag that prints Goodbye, NAME! on a line after the greeting. cargo test -q passes.
The change adds a bye option to Options and the --bye case in parse_args in src/lib.rs. It also adds a parse test. In src/main.rs, after the greeting lines, the flag prints the library's existing farewell(&name), using the same name as the greeting.
I asked #62's agent which name to use for the greeting function, but no answer had arrived when I finished. The change doesn't depend on the answer. main.rs already calls greeting_in, and --bye calls farewell. Neither of those is the function #62 renames (greeting to greet).