Factor out ServeProto::BasicClientConnection::buildDerivationRequest

For Hydra.

src/libstore/legacy-ssh-store.cc

@@ -238,16 +238,16 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
 
 private:
 
-    void putBuildSettings(Connection & conn)
+    ServeProto::BasicClientConnection::BuildOptions buildSettings()
     {
-        conn.putBuildSettings({
+        return {
             .maxSilentTime = settings.maxSilentTime,
             .buildTimeout = settings.buildTimeout,
             .repeats = 0, // buildRepeat hasn't worked for ages anyway
             .maxLogSize = settings.maxLogSize,
             .enforceDeterminism = 0,
             .keepFailed = settings.keepFailed,
-        });
+        };
     }
 
 public:
@@ -257,14 +257,7 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
     {
         auto conn(connections->get());
 
-        conn->to
-            << ServeProto::Command::BuildDerivation
-            << printStorePath(drvPath);
-        writeDerivation(conn->to, *this, drv);
-
-        putBuildSettings(*conn);
-
-        conn->to.flush();
+        conn->buildDerivationRequest(*this, drvPath, drv, buildSettings());
 
         return ServeProto::Serialise<BuildResult>::read(*this, *conn);
     }
@@ -294,7 +287,7 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
         }
         conn->to << ss;
 
-        putBuildSettings(*conn);
+        conn->putBuildSettings(buildSettings());
 
         conn->to.flush();
 

src/libstore/serve-protocol-impl.cc

@@ -1,4 +1,6 @@
 #include "serve-protocol-impl.hh"
+#include "build-result.hh"
+#include "derivations.hh"
 
 namespace nix {
 
@@ -36,4 +38,20 @@ void ServeProto::BasicClientConnection::putBuildSettings(
     }
 }
 
+
+void ServeProto::BasicClientConnection::buildDerivationRequest(
+    const Store & store,
+    const StorePath & drvPath, const BasicDerivation & drv,
+    const ServeProto::BasicClientConnection::BuildOptions & options)
+{
+    to
+        << ServeProto::Command::BuildDerivation
+        << store.printStorePath(drvPath);
+    writeDerivation(to, store, drv);
+
+    putBuildSettings(options);
+
+    to.flush();
+}
+
 }

src/libstore/serve-protocol-impl.hh

@@ -108,6 +108,15 @@ struct ServeProto::BasicClientConnection
     };
 
     void putBuildSettings(const BuildOptions & options);
+
+    /**
+     * Just the request half, because Hydra may do other things between
+     * issuing the request and reading the `BuildResult` response.
+     */
+    void buildDerivationRequest(
+        const Store & store,
+        const StorePath & drvPath, const BasicDerivation & drv,
+        const ServeProto::BasicClientConnection::BuildOptions & options);
 };
 
 }