Fix read-manifest summary printing under cargo --list

Author: dwijnand

src/bin/cargo/cli.rs

@@ -72,6 +72,7 @@ Run with 'cargo -Z [FLAG] [SUBCOMMAND]'"
             match command {
                 CommandInfo::BuiltIn { name, about } => {
                     let summary = about.unwrap_or_default();
+                    let summary = summary.lines().next().unwrap_or(&summary); // display only the first line
                     println!("    {:<20} {}", name, summary)
                 }
                 CommandInfo::External { name, path } => {

src/bin/cargo/commands/read_manifest.rs

@@ -5,8 +5,11 @@ use cargo::print_json;
 pub fn cli() -> App {
     subcommand("read-manifest")
         .about(
-            "Deprecated, use `cargo metadata --no-deps` instead.
-Print a JSON representation of a Cargo.toml manifest.",
+            "\
+Print a JSON representation of a Cargo.toml manifest.
+
+Deprecated, use `cargo metadata --no-deps` instead.\
+",
         )
         .arg_manifest_path()
 }

tests/testsuite/cargo_command.rs

@@ -70,6 +70,12 @@ fn list_commands_with_descriptions() {
         "missing build, with description: {}",
         output
     );
+    // assert read-manifest prints the right one-line description followed by another command, indented.
+    assert!(
+        output.contains("\n    read-manifest        Print a JSON representation of a Cargo.toml manifest.\n    "),
+        "missing build, with description: {}",
+        output
+    );
 }
 
 #[test]