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, 10 insertions, 0 deletions

diff --git a/nix/libstore/builtins.cc b/nix/libstore/builtins.cc
index 605e44079a..32af767dc4 100644
--- a/nix/libstore/builtins.cc
+++ b/nix/libstore/builtins.cc
@@ -66,4 +66,14 @@ derivationBuilder lookupBuiltinBuilder(const std::string & name)
 	return NULL;
 }
 
+std::list<std::string> builtinBuilderNames()
+{
+    std::list<std::string> result;
+    for(auto&& iter: builtins)
+    {
+	result.push_back(iter.first);
+    }
+    return result;
+}
+
 }