Don't make it an error for the self-update hash to be wrong

We've got problems with the updater and its hash being out
of sync. Thes patch considers a hash failure here a temporary
problem, prints a status message and exits with success.

cc #346

src/rustup-cli/self_update.rs

@@ -35,7 +35,6 @@ use itertools::Itertools;
 use rustup::{NotifyHandler};
 use errors::*;
 use rustup_dist::dist;
-use rustup_dist;
 use rustup_utils::utils;
 use openssl::crypto::hash::{Type, Hasher};
 use std::env;
@@ -1077,11 +1076,8 @@ pub fn prepare_update() -> Result<Option<PathBuf>> {
 
     // Check that hash is correct
     if latest_hash != download_hash {
-        return Err(ErrorKind::Dist(rustup_dist::ErrorKind::ChecksumFailed {
-            url: url,
-            expected: latest_hash,
-            calculated: download_hash,
-        }).into());
+        info!("update not yet available. bug #364");
+        return Ok(None);
     }
 
     // Mark as executable

tests/cli-self-update.rs

@@ -22,10 +22,9 @@ use std::process::Command;
 use rustup_mock::clitools::{self, Config, Scenario,
                                expect_ok, expect_ok_ex,
                                expect_stdout_ok,
+                               expect_stderr_ok,
                                expect_err, expect_err_ex,
                                this_host_triple};
-#[cfg(windows)]
-use rustup_mock::clitools::expect_stderr_ok;
 use rustup_mock::dist::{create_hash, calc_hash};
 use rustup_mock::{get_path, restore_path};
 use rustup_utils::raw;
@@ -520,6 +519,7 @@ info: rustup is up to date
 }
 
 #[test]
+#[ignore] // Workaround for #346
 fn update_bad_hash() {
     update_setup(&|config, self_dist| {
         expect_ok(config, &["rustup-init", "-y"]);
@@ -537,6 +537,25 @@ fn update_bad_hash() {
     });
 }
 
+// Workaround for #346
+#[test]
+fn update_hash_drift() {
+    update_setup(&|config, self_dist| {
+        expect_ok(config, &["rustup-init", "-y"]);
+
+        let ref trip = this_host_triple();
+        let ref dist_dir = self_dist.join(&format!("{}", trip));
+        let ref dist_hash = dist_dir.join(&format!("rustup-init{}.sha256", EXE_SUFFIX));
+
+        let ref some_other_file = config.distdir.join("dist/channel-rust-nightly.toml");
+
+        create_hash(some_other_file, dist_hash);
+
+        expect_stderr_ok(config, &["rustup", "self", "update"],
+                         "update not yet available");
+    });
+}
+
 #[test]
 fn update_hash_file_404() {
     update_setup(&|config, self_dist| {