diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/diffpatcher/rebase.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/diffpatcher/rebase.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,36 @@
+"use strict";
+
+var nil = {}
+var owns = ({}).hasOwnProperty
+
+function rebase(result, parent, delta) {
+  var key, current, previous, update
+  for (key in parent) {
+    if (owns.call(parent, key)) {
+      previous = parent[key]
+      update = owns.call(delta, key) ? delta[key] : nil
+      if (previous === null) continue
+      else if (previous === void(0)) continue
+      else if (update === null) continue
+      else if (update === void(0)) continue
+      else result[key] = previous
+    }
+  }
+  for (key in delta) {
+    if (owns.call(delta, key)) {
+      update = delta[key]
+      current = owns.call(result, key) ? result[key] : nil
+      if (current === update) continue
+      else if (update === null) continue
+      else if (update === void(0)) continue
+      else if (current === nil) result[key] = update
+      else if (typeof(update) !== "object") result[key] = update
+      else if (typeof(current) !== "object") result[key] = update
+      else result[key]= rebase({}, current, update)
+    }
+  }
+
+  return result
+}
+
+module.exports = rebase