shredder: do not hash single-file groups unless --hash-uniques

Fixes #614 (albeit in a hacky way).

Author: intelfx

lib/shredder.c

@@ -836,6 +836,10 @@ static void rm_shred_group_update_status(RmShredGroup *group) {
         // hashes complete
         return;
     }
+    if (!(group->num_files >= 2) && !group->session->cfg->hash_uniques) {
+        // no hashing required (yet)
+        return;
+    }
     if(!rm_shred_group_qualifies(group) && !group->session->cfg->hash_uniques &&
        !group->session->cfg->hash_unmatched) {
         // no hashing requred (yet)