nix: Don't require --experimental-features=nix-command for some subcommands

src/nix/main.cc

@@ -167,12 +167,15 @@ void mainWrapped(int argc, char * * argv)
 
     args.parseCmdline(argvToStrings(argc, argv));
 
-    settings.requireExperimentalFeature("nix-command");
-
     initPlugins();
 
     if (!args.command) args.showHelpAndExit();
 
+    if (args.command->first != "repl"
+        && args.command->first != "doctor"
+        && args.command->first != "upgrade-nix")
+        settings.requireExperimentalFeature("nix-command");
+
     Finally f([]() { stopProgressBar(); });
 
     startProgressBar(args.printBuildLogs);