message: Don't print crates.io-index URL when Updating
  Following the lead from PackageId's Display, only display the registry's
  URL if it's not the default registry (aka crates.io).
  Before:
  $ cargo install lazy_static
  Updating registry `https://github.com/rust-lang/crates.io-index`
  After:
  $ dcargo install lazy_static
  Updating registry
diff: @@ -210,8 +210,12 @@ impl SourceId {
  }
  pub fn display_registry(&self) -> String {
  + if self.is_default_registry() {
  + "registry".to_string()
  + } else {
  format!("registry `{}`", self.url())
  }
  + }
  /// Is this source from a filesystem path
  pub fn is_path(&self) -> bool {
  