Merge pull request #1532 from NixOS/proto-dedup

Deduplicate protocol code more with `ServeProto::BasicClientConnection`

Author: Ericson2314

src/hydra-queue-runner/build-remote.cc

@@ -103,9 +103,9 @@ static void copyClosureTo(
     std::unique_lock<std::timed_mutex> sendLock(conn.machine->state->sendLock,
         std::chrono::seconds(600));
 
-    conn.to << ServeProto::Command::ImportPaths;
-    destStore.exportPaths(missing, conn.to);
-    conn.to.flush();
+    conn.importPaths(destStore, [&](Sink & sink) {
+        destStore.exportPaths(missing, sink);
+    });
 
     if (readInt(conn.from) != 1)
         throw Error("remote machine failed to import closure");
@@ -298,11 +298,10 @@ static void copyPathFromRemote(
               lambda function only gets executed if someone tries to read
               from source2, we will send the command from here rather
               than outside the lambda. */
-          conn.to << ServeProto::Command::DumpStorePath << localStore.printStorePath(info.path);
-          conn.to.flush();
-
-          TeeSource tee(conn.from, sink);
-          extractNarData(tee, localStore.printStorePath(info.path), narMembers);
+          conn.narFromPath(localStore, info.path, [&](Source & source) {
+              TeeSource tee(source, sink);
+              extractNarData(tee, localStore.printStorePath(info.path), narMembers);
+          });
       });
 
       destStore.addToStore(info, *source2, NoRepair, NoCheckSigs);