clarify error propogation

src/tree.c

@@ -149,7 +149,7 @@ static int tree_key_search(
 	/* Initial homing search; find an entry on the tree with
 	 * the same prefix as the filename we're looking for */
 	if (git_vector_bsearch2(&homing, entries, &homing_search_cmp, &ksearch) < 0)
-		return GIT_ENOTFOUND;
+		return GIT_ENOTFOUND; /* just a signal error; not passed back to user */
 
 	/* We found a common prefix. Look forward as long as
 	 * there are entries that share the common prefix */