Don't access the Internet in the check_updates tests

Previously, three of the tests in `cli-exact.rs` would try to connect to the
Internet, or fail if the Internet wasn't available:

*   `check_updates_with_update`
*   `check_updates_none`
*   `check_updates_some`

This is because all three tests would run `rustup check`, and because the tests
weren't overriding the value of `RUSTUP_UPDATE_ROOT`, they'd go out to the
Internet to try to download self-updates.

The new helper mimics the behaviour of the `self_update_setup()` helper in the
same file.  It creates a mock self-update server in a local directory, and
points rustup to the directory using a `file://` URL.  When it tries to get
self-updates as part of `rustup check`, it only fetches from that directory.

Author: alexwlchan

tests/cli-exact.rs

@@ -4,8 +4,8 @@
 pub mod mock;
 
 use crate::mock::clitools::{
-    self, expect_err_ex, expect_ok, expect_ok_ex, expect_stdout_ok, self_update_setup,
-    set_current_dist_date, Config, Scenario,
+    self, check_update_setup, expect_err_ex, expect_ok, expect_ok_ex, expect_stdout_ok,
+    self_update_setup, set_current_dist_date, Config, Scenario,
 };
 use rustup::for_host;
 use rustup::test::this_host_triple;
@@ -68,7 +68,7 @@ fn update_again() {
 
 #[test]
 fn check_updates_none() {
-    setup(&|config| {
+    check_update_setup(&|config| {
         set_current_dist_date(config, "2015-01-01");
         expect_ok(config, &["rustup", "update", "stable", "--no-self-update"]);
         expect_ok(config, &["rustup", "update", "beta", "--no-self-update"]);
@@ -88,7 +88,7 @@ nightly-{0} - Up to date : 1.2.0 (hash-nightly-1)
 
 #[test]
 fn check_updates_some() {
-    setup(&|config| {
+    check_update_setup(&|config| {
         set_current_dist_date(config, "2015-01-01");
         expect_ok(config, &["rustup", "update", "stable", "--no-self-update"]);
         expect_ok(config, &["rustup", "update", "beta", "--no-self-update"]);
@@ -151,7 +151,7 @@ fn check_updates_self_no_change() {
 
 #[test]
 fn check_updates_with_update() {
-    setup(&|config| {
+    check_update_setup(&|config| {
         set_current_dist_date(config, "2015-01-01");
         expect_ok(config, &["rustup", "update", "stable", "--no-self-update"]);
         expect_ok(config, &["rustup", "update", "beta", "--no-self-update"]);

tests/mock/clitools.rs

@@ -189,6 +189,33 @@ pub fn setup(s: Scenario, f: &dyn Fn(&mut Config)) {
     assert!(!PathBuf::from("./bogus-cargo-home").exists());
 }
 
+pub fn check_update_setup(f: &dyn Fn(&mut Config)) {
+    let version = env!("CARGO_PKG_VERSION");
+
+    setup(Scenario::ArchivesV2, &|config| {
+        // Create a mock self-update server
+        let self_dist_tmp = tempfile::Builder::new()
+            .prefix("self_dist")
+            .tempdir()
+            .unwrap();
+        let self_dist = self_dist_tmp.path();
+
+        let trip = this_host_triple();
+        let dist_dir = self_dist.join(&format!("archive/{}/{}", version, trip));
+        let dist_exe = dist_dir.join(&format!("rustup-init{}", EXE_SUFFIX));
+        let rustup_bin = config.exedir.join(&format!("rustup-init{}", EXE_SUFFIX));
+
+        fs::create_dir_all(dist_dir).unwrap();
+        output_release_file(self_dist, "1", version);
+        fs::copy(&rustup_bin, &dist_exe).unwrap();
+
+        let root_url = format!("file://{}", self_dist.display());
+        config.rustup_update_root = Some(root_url);
+
+        f(config);
+    });
+}
+
 pub fn self_update_setup(f: &dyn Fn(&Config, &Path), version: &str) {
     setup(Scenario::SimpleV2, &|config| {
         // Create a mock self-update server