Merge branch 'usage-text'

src/swab.rs

@@ -35,7 +35,7 @@ fn oserr(s: &str, e: Error) -> ExitCode {
 }
 
 fn usage(s: &str) -> ExitCode {
-	eprintln!("Usage: {} (-f) (-w [wordsize])", s);
+	eprintln!("Usage: {} [-f] [-w word_size]", s);
 	ExitCode::from(EX_USAGE as u8)
 }