--no-push and remote.name.annex-push prevent exporting trees to special remotes

Users may want sync to only export, or only import and this is broadly
analagous to push and pull, so it makes sense to use the same
configuration for it.

Assistant/Threads/Exporter.hs

@@ -64,7 +64,7 @@ exportToRemotes rs = do
 		forM rs $ \r -> do
 			Annex.changeState $ \st -> st { Annex.errcounter = 0 }
 			start <- liftIO getCurrentTime
-			void $ Command.Sync.seekExportContent rs
+			void $ Command.Sync.seekExportContent Nothing rs
 				=<< getCurrentBranch
 			-- Look at command error counter to see if the export
 			-- didn't work.