ci: Further tone down the test verbosity.

When `--quiet` is passed to rustbuild, suppress rustdoc test output unless
failure.

Added a `--quiet` flag to `tidy`, which suppresses the features table.

The actual `--quiet` flag is enabled in #42354.

Since details of failed tests will still be printed, and the name of slow
tests taking >60 to runtime will also be printed, the debugging difficulty
caused by information loss should be minimal; but it is very worthwhile to
keep the log under 10000 lines on Travis CI so that common errors can be
spotted without reading the raw log.

src/bootstrap/check.rs

@@ -132,6 +132,9 @@ pub fn tidy(build: &Build, host: &str) {
     if !build.config.vendor {
         cmd.arg("--no-vendor");
     }
+    if build.config.quiet_tests {
+        cmd.arg("--quiet");
+    }
     build.run(&mut cmd);
 }
 
@@ -355,13 +358,14 @@ fn markdown_test(build: &Build, compiler: &Compiler, markdown: &Path) {
     cmd.arg(markdown);
     cmd.env("RUSTC_BOOTSTRAP", "1");
 
-    let mut test_args = build.flags.cmd.test_args().join(" ");
+    let test_args = build.flags.cmd.test_args().join(" ");
-    if build.config.quiet_tests {
-        test_args.push_str(" --quiet");
-    }
     cmd.arg("--test-args").arg(test_args);
 
-    build.run(&mut cmd);
+    if build.config.quiet_tests {
+        build.run_quiet(&mut cmd);
+    } else {
+        build.run(&mut cmd);
+    }
 }
 
 /// Run all unit tests plus documentation tests for an entire crate DAG defined

src/tools/tidy/src/features.rs

@@ -49,7 +49,7 @@ pub struct Feature {
     pub has_gate_test: bool,
 }
 
-pub fn check(path: &Path, bad: &mut bool) {
+pub fn check(path: &Path, bad: &mut bool, quiet: bool) {
     let mut features = collect_lang_features(path);
     assert!(!features.is_empty());
 
@@ -134,6 +134,10 @@ pub fn check(path: &Path, bad: &mut bool) {
     if *bad {
         return;
     }
+    if quiet {
+        println!("* {} features", features.len());
+        return;
+    }
 
     let mut lines = Vec::new();
     for (name, feature) in features.iter() {

src/tools/tidy/src/main.rs

@@ -57,11 +57,12 @@ fn main() {
     let args: Vec<String> = env::args().skip(1).collect();
 
     let mut bad = false;
+    let quiet = args.iter().any(|s| *s == "--quiet");
     bins::check(&path, &mut bad);
     style::check(&path, &mut bad);
     errors::check(&path, &mut bad);
     cargo::check(&path, &mut bad);
-    features::check(&path, &mut bad);
+    features::check(&path, &mut bad, quiet);
     pal::check(&path, &mut bad);
     unstable_book::check(&path, &mut bad);
     if !args.iter().any(|s| *s == "--no-vendor") {