协议缓冲区3部分更新

Question

I am trying to implement partial update with Protocol Buffers 3 (using Go). The problem is that in some cases it's not possible to distinguish default (empty) values and the same values set on purpose (like a description set to an empty string to clear it).

After some digging I found reference to FieldMasks in this issue which explains that such values cannot be distinguished, but an incremental update is possible using FieldMasks.

I tried to find some documentation or guide explaining how to use FieldMasks, but I couldn't.

So the question is: how can I achieve partial update with proto3 (using FieldMasks)?

Any help is appreciated.