message: Add built-in alias shadowing not warning test
diff: @@ -150,6 +150,30 @@ fn dependent_alias() {
  .run();
  }
  +#[cargo_test]
  +fn builtin_alias_shadowing_external_subcommand() {
  + let p = project()
  + .file("Cargo.toml", &basic_bin_manifest("foo"))
  + .file("src/main.rs", "fn main() {}")
  + .executable("cargo-t", "")
  + .build();
  +
  + let mut paths: Vec<_> = env::split_paths(&env::var_os("PATH").unwrap_or_default()).collect();
  + paths.push(p.root());
  + let path = env::join_paths(paths).unwrap();
  +
  + p.cargo("t")
  + .env("PATH", &path)
  + .with_stderr(
  + "\
  +[COMPILING] foo v0.5.0 [..]
  +[FINISHED] test [unoptimized + debuginfo] target(s) in [..]
  +[RUNNING] unittests src/main.rs [..]
  +",
  + )
  + .run();
  +}
  +
  #[cargo_test]
  fn alias_shadowing_external_subcommand() {
  let echo = echo_subcommand();
  