notmuch: add TODO

notmuch/src/lib.rs

@@ -518,6 +518,7 @@ impl Notmuch {
     }
 
     pub fn count(&self, query: &str) -> Result<usize, NotmuchError> {
+        // TODO: compare speed of notmuch count for * w/ and w/o --output=threads
         let res = self.run_notmuch(["count", "--output=threads", query])?;
         // Strip '\n' from res.
         let s = std::str::from_utf8(&res[..res.len() - 1])?;