signature of pb2json [etc]: why not const ref instead of const pointer?

[timotheecour]

why
void pb2json(const google::protobuf::Message* msg, std::string& str);
instead of:
void pb2json(const google::protobuf::Message& msg, std::string& str);

(or even:
void pb2json(const google::protobuf::Message& msg, std::string* str);
to make it clear str is being modified)

[yinqiwen]

yes, it is much better :)