Add docs command
This PR adds "rustup docs" command which is aliased to "rustup doc".
Closes
@@ -304,6 +304,7 @@ pub fn cli() -> App<'static, 'static> {
.arg(Arg::with_name("command")
.required(true)))
.subcommand(SubCommand::with_name("doc")
+ .alias("docs")
.about("Open the documentation for the current toolchain")
.after_help(DOC_HELP)
.arg(Arg::with_name("book")
