test: add test for rustup toolchain install --no-update

Author: nozwock

tests/suite/cli-ui/rustup/rustup_toolchain_cmd_install_cmd_help_flag_stdout.toml

@@ -15,6 +15,7 @@ Options:
   -t, --target <TARGET>        Comma-separated list of targets to be added on installation
       --no-self-update         Don't perform self update when running the `rustup toolchain install`
                                command
+      --no-update              Don't try to update the installed toolchain
       --force                  Force an update, even if some components are missing
       --allow-downgrade        Allow rustup to downgrade the toolchain to satisfy your component
                                choice

tests/suite/cli_rustup.rs

@@ -1737,6 +1737,32 @@ info: it's active because: overridden by '[TOOLCHAIN_FILE]'
         .is_ok();
 }
 
+#[tokio::test]
+async fn toolchain_install_no_change_with_no_update() {
+    let mut cx = CliTestContext::new(Scenario::None).await;
+
+    {
+        let cx = cx.with_dist_dir(Scenario::ArchivesV2_2015_01_01);
+        cx.config
+            .expect(["rustup", "toolchain", "add", "stable"])
+            .await
+            .is_ok();
+    }
+
+    let cx = cx.with_dist_dir(Scenario::SimpleV2);
+    cx.config
+        .expect(["rustup", "install", "--no-update", "stable"])
+        .await
+        .with_stdout(snapbox::str![[r#"
+
+  stable-[HOST_TRIPLE] unchanged - 1.0.0 (hash-stable-1.0.0)
+
+
+"#]])
+        .with_stderr(snapbox::str![[""]])
+        .is_ok();
+}
+
 #[tokio::test]
 async fn toolchain_update_is_like_update() {
     let cx = CliTestContext::new(Scenario::SimpleV2).await;