DebugStackTracker class in one place

src/libcmd/command.cc

@@ -75,6 +75,8 @@ ref<EvalState> EvalCommand::getEvalState()
 
                 printStaticEnvBindings(expr);
 
+                std::cout << evalState->vCallFlake << std::endl;
+
                 std::cout << "expr: " << std::endl;
                 expr.show(std::cout);
                 std::cout << std::endl;

src/libcmd/repl.cc

@@ -451,6 +451,7 @@ bool NixRepl::processLine(string line)
         }
         else if (arg == "error") {
           if (this->debugError.has_value()) {
+            // TODO user --show-trace setting?
             showErrorInfo(std::cout, (*debugError)->info(), true);
           }
           else