Create `worker_proto::{Read,Write}Conn`

Pass this around instead of `Source &` and `Sink &` directly. This will
give us something to put the protocol version on once the time comes.

To do this ergonomically, we need to expose `RemoteStore::Connection`,
so do that too. Give it some more API docs while we are at it.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 1a946e3d2..5e37f7ecb 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -1151,9 +1151,11 @@ HookReply DerivationGoal::tryBuildHook()
         throw;
     }
 
+    WorkerProto::WriteConn conn { hook->sink };
+
     /* Tell the hook all the inputs that have to be copied to the
        remote system. */
-    WorkerProto::write(worker.store, hook->sink, inputPaths);
+    WorkerProto::write(worker.store, conn, inputPaths);
 
     /* Tell the hooks the missing outputs that have to be copied back
        from the remote system. */
@@ -1164,7 +1166,7 @@ HookReply DerivationGoal::tryBuildHook()
             if (buildMode != bmCheck && status.known && status.known->isValid()) continue;
             missingOutputs.insert(outputName);
         }
-        WorkerProto::write(worker.store, hook->sink, missingOutputs);
+        WorkerProto::write(worker.store, conn, missingOutputs);
     }
 
     hook->sink = FdSink();