message: Improve the description of Config.home_path
  I poked around and it seems it's not the user's home directory but Cargo
  home (which may or may not be in user's home).
diff: @@ -122,7 +122,7 @@ macro_rules! get_value_typed {
  /// relating to cargo itself.
  #[derive(Debug)]
  pub struct Config {
  - /// The location of the user's 'home' directory. OS-dependent.
  + /// The location of the user's Cargo home directory. OS-dependent.
  home_path: Filesystem,
  /// Information about how to write messages to the shell
  shell: RefCell<Shell>,
  