jj: check first line using .lines()

config/jj/config.toml

@@ -56,7 +56,7 @@ if(root,
       separate(" ",
         if(empty, label("empty", "(empty)")),
         if(description,
-          description.first_line() ++ if(description.first_line().len() < description.trim_end().len(),
+          description.first_line() ++ if(description.lines().len() > 1,
             label("rest", "\n\t" ++ description.substr(description.first_line().len() + 2, -1).first_line())
           ),
           label(if(empty, "empty"), description_placeholder),