Crates.io Username Concept Introduced

// This program demonstrates the problem that the new crates.io username concept
// solves: two users with the same GitHub name cannot both use that name on crates.io.
// Since the change is not yet in the current Rust release, we simply illustrate
// the issue with a mock example.

fn main() {
    // Two users with the same GitHub username "alice"
    let github_user_a = "alice";
    let github_user_b = "alice";

    // On crates.io before the change, both would collide
    if github_user_a == github_user_b {
        println!("Collision: both users would have the same crates.io name.");
    } else {
        println!("No collision.");
    }

    // After the change, each can choose a distinct crates.io username
    let crates_io_username_a = "alice_dev";
    let crates_io_username_b = "alice_prod";

    if crates_io_username_a != crates_io_username_b {
        println!("No collision after username decoupling: {} vs {}", crates_io_username_a, crates_io_username_b);
    }
}