Add up as an alias of update

Author: jbalintbiro

src/cli/rustup_mode.rs

@@ -313,7 +313,7 @@ pub(crate) fn cli() -> App<'static, 'static> {
         .subcommand(
             SubCommand::with_name("update")
                 .about("Update Rust toolchains and rustup")
-                .aliases(&["upgrade"])
+                .aliases(&["upgrade", "up"])
                 .after_help(UPDATE_HELP)
                 .arg(
                     Arg::with_name("toolchain")

tests/cli-exact.rs

@@ -170,6 +170,9 @@ fn check_updates_none() {
         expect_ok(config, &["rustup", "upgrade", "stable"]);
         expect_ok(config, &["rustup", "upgrade", "beta"]);
         expect_ok(config, &["rustup", "upgrade", "nightly"]);
+        expect_ok(config, &["rustup", "up", "stable"]);
+        expect_ok(config, &["rustup", "up", "beta"]);
+        expect_ok(config, &["rustup", "up", "nightly"]);
         expect_stdout_ok(
             config,
             &["rustup", "check"],