Extend GetFileNode function to check for unique file nodes

This is useful for the command line interfaces to detect the desired node.

controlservice.proto

@@ -29,6 +29,11 @@ message SwitchPhaseResponse {
   string error = 2;
 }
 
+message GetFileNodeMessage {
+  FileNode fileNode = 1;
+  bool uniqueNode = 2;
+}
+
 message StatusMessage {
   bool phase = 1;
   bool switch = 2;
@@ -58,7 +63,7 @@ service ControlService {
   rpc Quit(QuitMessage) returns (QuitResponse) {}
   rpc SwitchPhase(SwitchPhaseMessage) returns (SwitchPhaseResponse) {}
   rpc GetPackageNode(PackageNode) returns (PackageNode) {}
-  rpc GetFileNode(FileNode) returns (stream FileNode) {}
+  rpc GetFileNode(GetFileNodeMessage) returns (stream FileNode) {}
   rpc GetDiagnosticNode(DiagnosticNode) returns (stream DiagnosticNode) {}
   rpc Status(StatusMessage) returns (StatusResponse) {}
   rpc SubscribeEvents(EventMessage) returns (stream Event) {}