Switchable the main branch on network graph

app/controllers/graph_controller.rb

@@ -0,0 +1,18 @@
+class GraphController < ProjectResourceController
+  include ExtractsPath
+
+  # Authorize
+  before_filter :authorize_read_project!
+  before_filter :authorize_code_access!
+  before_filter :require_non_empty_project
+
+  def show
+    respond_to do |format|
+      format.html
+      format.json do
+        graph = Gitlab::Graph::JsonBuilder.new(project, @ref)
+        render :json => graph.to_json
+      end
+    end
+  end
+end