message: Don't warn about shadowing in the case where the alias is built-in
diff: @@ -262,10 +262,11 @@ To pass the arguments to the subcommand, remove `--`",
  }
  (None, Ok(None)) => {}
  (None, Ok(Some(alias))) => {
  - // Check if this alias is shadowing an external subcommand
  + // Check if a user-defined alias is shadowing an external subcommand
  // (binary of the form `cargo-<subcommand>`)
  // Currently this is only a warning, but after a transition period this will become
  // a hard error.
  + if super::builtin_aliases_execs(cmd).is_none() {
  if let Some(path) = super::find_external_subcommand(config, cmd) {
  config.shell().warn(format!(
  "\
  @@ -276,6 +277,7 @@ For more information, see issue #10049 <https://github.com/rust-lang/cargo/issue
  path.display(),
  ))?;
  }
  + }
  let mut alias = alias
  .into_iter()
  