cli: add docs comment for --output option

Author: devmatteini

src/cli/root_command.rs

@@ -27,6 +27,9 @@ pub enum Command {
         #[structopt(short = "s", long = "select")]
         select: Option<String>,
 
+        /// Save asset to custom path
+        ///
+        /// Default path is current working directory and the name of the asset
         #[structopt(short = "o", long = "output", parse(from_os_str))]
         output: Option<PathBuf>,
     },