daemon: Add 'built-in-builders' RPC.

* nix/libstore/builtins.cc (builtinBuilderNames): New function.
* nix/libstore/builtins.hh (builtinBuilderNames): New declaration.
* nix/libstore/worker-protocol.hh (PROTOCOL_VERSION): Bump to 0x160.
(WorkerOp)[wopBuiltinBuilders]: New value.
* nix/nix-daemon/nix-daemon.cc (performOp): Handle it.
* guix/store.scm (operation-id)[built-in-builders]: New value.
* guix/store.scm (read-arg): Add 'string-list'.
(built-in-builders): New procedure.
* tests/derivations.scm ("built-in-builders"): New test.

1 files changed, 9 insertions, 0 deletions

diff --git a/nix/nix-daemon/nix-daemon.cc b/nix/nix-daemon/nix-daemon.cc
index 35c284f7e1..9b29b3e91d 100644
--- a/nix/nix-daemon/nix-daemon.cc
+++ b/nix/nix-daemon/nix-daemon.cc
@@ -6,6 +6,7 @@
 #include "archive.hh"
 #include "affinity.hh"
 #include "globals.hh"
+#include "builtins.hh"
 
 #include <algorithm>
 
@@ -671,6 +672,14 @@ static void performOp(bool trusted, unsigned int clientVersion,
         break;
     }
 
+    case wopBuiltinBuilders: {
+	startWork();
+	auto names = builtinBuilderNames();
+	stopWork();
+	writeStrings(names, to);
+	break;
+    }
+
     default:
         throw Error(format("invalid operation %1%") % op);
     }