Remove redundant provenance field from {Read,Write}Conn

This makes `nix copy` from ssh-ng to the daemon preserve provenance,
because in combination with the previous commits,
RemoteStore::addToStoreMultiple() now sends provenance if the daemon
supports it.

Fixes #369.

Author: edolstra

src/libstore/include/nix/store/worker-protocol-connection.hh

@@ -36,7 +36,6 @@ struct WorkerProto::BasicConnection
         return WorkerProto::ReadConn{
             .from = from,
             .version = protoVersion,
-            .provenance = protoVersion.features.contains(WorkerProto::featureProvenance),
         };
     }
 
@@ -53,7 +52,6 @@ struct WorkerProto::BasicConnection
         return WorkerProto::WriteConn{
             .to = to,
             .version = protoVersion,
-            .provenance = protoVersion.features.contains(WorkerProto::featureProvenance),
         };
     }
 };

src/libstore/include/nix/store/worker-protocol.hh

@@ -122,7 +122,6 @@ struct WorkerProto
         Source & from;
         const Version & version;
         bool shortStorePaths = false;
-        bool provenance = false;
     };
 
     /**
@@ -134,7 +133,6 @@ struct WorkerProto
         Sink & to;
         const Version & version;
         bool shortStorePaths = false;
-        bool provenance = false;
     };
 
     /**

src/libstore/worker-protocol.cc

@@ -353,7 +353,7 @@ UnkeyedValidPathInfo WorkerProto::Serialise<UnkeyedValidPathInfo>::read(const St
         info.sigs = WorkerProto::Serialise<std::set<Signature>>::read(store, conn);
         info.ca = ContentAddress::parseOpt(readString(conn.from));
     }
-    if (conn.provenance)
+    if (conn.version.features.contains(WorkerProto::featureProvenance))
         info.provenance = Provenance::from_json_str_optional(readString(conn.from));
     return info;
 }
@@ -370,7 +370,7 @@ void WorkerProto::Serialise<UnkeyedValidPathInfo>::write(
         WorkerProto::write(store, conn, pathInfo.sigs);
         conn.to << renderContentAddress(pathInfo.ca);
     }
-    if (conn.provenance)
+    if (conn.version.features.contains(WorkerProto::featureProvenance))
         conn.to << (pathInfo.provenance ? pathInfo.provenance->to_json_str() : "");
 }