check remote prior to mount

repertory/repertory/include/cli/mount.hpp

@@ -121,11 +121,32 @@ mount(std::vector<const char *> args, std::string data_directory,
             << " Drive" << std::endl;
   if (prov == provider_type::remote) {
     try {
+      constexpr const std::uint8_t retry_count{30U};
+
       auto remote_cfg = config.get_remote_config();
       remote_cfg.host_name_or_ip = remote_host;
       remote_cfg.api_port = remote_port;
       config.set_remote_config(remote_cfg);
 
+      std::cout << "Connecting to remote [" << remote_host << ':' << remote_port
+                << "] ..." << std::flush;
+      auto online{false};
+      for (std::uint8_t retry{0U}; not online && retry < retry_count; ++retry) {
+        online = remote_client(config).check() == 0;
+        if (online) {
+          continue;
+        }
+        std::cout << "." << std::flush;
+        std::this_thread::sleep_for(1s);
+      }
+
+      if (not online) {
+        std::cerr << " failed! remote host is offline." << std::endl;
+        return exit_code::communication_error;
+      }
+
+      std::cout << " done!" << std::endl;
+
       remote_drive drive(
           config,
           [&config]() -> std::unique_ptr<remote_instance> {