tree f3d152d3c12559d9e7d9d6d2dee98b2c76cfe889
parent af5984f9c65738299ca1f0a21cdcd34a4002a0c0
author Shawn O. Pearce <sop@google.com> 1328133126 -0800
committer Shawn O. Pearce <sop@google.com> 1328134711 -0800

Only make primary key protobuf fields required

The primary key is extremely hard to change, so make it required
as the fields must all be not null and populated in order to have
a valid entity.

Other fields may have been added after instances of the entity were
already created. Permit those to be optional, so existing data does
not have to be modified before being used with the new definition.

Change-Id: I1865dffda7a5a4004fd77aa0a37aa1e3ae20976f