chore(rustfmt): remove executable path from usage string (rust-lang#5216)

* chore(rustfmt): remove executable path from usage string

* add unit test for usage string

* rename test and check usage text in a single assert

Author: tharun208

src/bin/main.rs

@@ -394,9 +394,8 @@ fn print_usage_to_stdout(opts: &Options, reason: &str) {
         format!("{}\n\n", reason)
     };
     let msg = format!(
-        "{}Format Rust code\n\nusage: {} [options] <file>...",
-        sep,
-        env::args_os().next().unwrap().to_string_lossy()
+        "{}Format Rust code\n\nusage: rustfmt [options] <file>...",
+        sep
     );
     println!("{}", opts.usage(&msg));
 }

tests/rustfmt/main.rs

@@ -106,3 +106,12 @@ fn inline_config() {
             && contains("format_strings = true")
     );
 }
+
+#[test]
+fn rustfmt_usage_text() {
+    let args = [
+        "--help",
+    ];
+    let (stdout, _) = rustfmt(&args);
+    assert!(stdout.contains(&format!("Format Rust code\n\nusage: rustfmt [options] <file>...")));
+}