prevent duplicated owners in metadata amendments

lib/deduplicate.js

@@ -0,0 +1,11 @@
+// remove duplicate elements in an array
+module.exports = function (O) {
+    // make a copy of the original array
+    var A = O.slice();
+    for (var i = 0; i < A.length; i++) {
+        for (var j = i + 1; j < A.length; j++) {
+            if (A[i] === A[j]) { A.splice(j--, 1); }
+        }
+    }
+    return A;
+};

lib/metadata.js

@@ -1,5 +1,7 @@
 var Meta = module.exports;
 
+var deduplicate = require("./deduplicate");
+
 /*  Metadata fields:
 
     * channel <STRING>
@@ -64,7 +66,7 @@ commands.RESET_OWNERS = function (meta, args) {
     }
 
     // overwrite the existing owners with the new one
-    meta.owners = args;
+    meta.owners = deduplicate(args);
 };
 
 commands.UPDATE_EXPIRATION = function () {