* Move addTempRoot() to the store API, and add another function

syncWithGC() to allow clients to register GC roots without needing
  write access to the global roots directory or the GC lock.

src/libstore/worker-protocol.hh

@@ -18,6 +18,8 @@ typedef enum {
     wopAddTextToStore,
     wopBuildDerivations,
     wopEnsurePath,
+    wopAddTempRoot,
+    wopSyncWithGC
 } WorkerOp;