feat: filename can be none

src/cmd_signfile.rs

@@ -101,7 +101,10 @@ impl Command for CommandImpl {
         });
 
         let sign_file_request = SignFileRequest {
-            filename: filename_opt,
+            filename: match filename_opt {
+                None => None,
+                Some(filename) => iff!(filename.is_empty(), None, Some(filename)),
+            },
             digest: file_digest.clone(),
             timestamp: SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap().as_millis() as i64,
             attributes: attributes_opt,