Proposal for deltas of messages within a RepeatedField

example.cs

var foo = new SimpleNestedMessage();
list.Add(foo);
// Generates:  new EventData { Action = AddList, EventContent = foo.toByteString() , Path = [1, 0]}  // 0 is the index of foo object
// Sets _root and _path in the foo instance
// if _root already exists throw exception, can't add message to two parents at once
foo.a = 10;
// Generates: new EventData { Action = Set, EventContent = 10 , Path = [1, 0, 1]}
foo.b = "hello";
// Generates: new EventData { Action = Set, EventContent = "hello" , Path = [1, 0, 2]}

var bar = new SimpleNestedMessage();
list.Insert(bar);
// Generates:  new EventData { Action = InsertList, Field = 0, EventContent = bar.toByteString() , Path = [1, 0]}  // 0 is the index of bar object
// Updates path on any objects that appear after bar, in this case foo, becomes index 1
// Sets _root and _path in the bar instance
// if _root already exists throw exception, can't add message to two parents at once

foo.a = 11;
// Generates:  new EventData { Action = Set, EventContent = 11 , Path = [1, 1, 1]}  // 1 is the index of foo object now

list.RemoveAt(0);
// Generates:  new EventData { Action = RemoveAtList, Path = [1, 0]}
// Updates path on any objects that appear after bar, in this case foo, becomes index 1
// clears _root & _path on the bar object

var baz = new SimpleNestedMessage();
list[0] = baz;
// Generates:  new EventData { Action = ReplaceList, EventContent = baz.toByteString() , Path = [1, 0]}
// clears _root & _path on the foo object
// Sets _root and _path in the baz instance
// if _root already exists throw exception, can't add message to two parents at once

simple.proto

message SimpleNestedMessage {
  int64 a = 1;
  string b = 2;
}

message SimpleList {
  repeated SimpleNestedMessage = 1;
}