Do not show "available paths" help in ./x.py clean

Author: tommyip

src/bootstrap/flags.rs

@@ -253,17 +253,18 @@ Arguments:
             }
         });
 
-        // All subcommands can have an optional "Available paths" section
+        // All subcommands except `clean` can have an optional "Available paths" section
         if matches.opt_present("verbose") {
             let config = Config::parse(&["build".to_string()]);
             let mut build = Build::new(config);
             metadata::build(&mut build);
 
             let maybe_rules_help = Builder::get_help(&build, subcommand.as_str());
             extra_help.push_str(maybe_rules_help.unwrap_or_default().as_str());
-        } else {
-            extra_help.push_str(format!("Run `./x.py {} -h -v` to see a list of available paths.",
-                     subcommand).as_str());
+        } else if subcommand.as_str() != "clean" {
+            extra_help.push_str(format!(
+                "Run `./x.py {} -h -v` to see a list of available paths.",
+                subcommand).as_str());
         }
 
         // User passed in -h/--help?
@@ -293,7 +294,7 @@ Arguments:
             }
             "clean" => {
                 if paths.len() > 0 {
-                    println!("\nclean takes no arguments\n");
+                    println!("\nclean does not take a path argument\n");
                     usage(1, &opts, &subcommand_help, &extra_help);
                 }