matchers: don't allow dead_code

lib/src/matchers.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#![allow(dead_code, missing_docs)]
+#![allow(missing_docs)]
 
 use std::collections::{HashMap, HashSet};
 use std::fmt::Debug;
@@ -369,6 +369,7 @@ impl RepoPathTree {
         })
     }
 
+    #[cfg(test)]
     fn add_dir(&mut self, dir: &RepoPath) {
         self.add(dir).is_dir = true;
     }