spdlog.patch

diff --git include/spdlog/cfg/env.h include/spdlog/cfg/env.h
index 6e554145..10a44dc5 100644
--- include/spdlog/cfg/env.h
+++ include/spdlog/cfg/env.h
@@ -25,8 +25,8 @@
 
 namespace spdlog {
 namespace cfg {
-inline void load_env_levels() {
-    auto env_val = details::os::getenv("SPDLOG_LEVEL");
+inline void load_env_levels(const char *env_var = "SPDLOG_LEVEL") {
+    auto env_val = details::os::getenv(env_var);
     if (!env_val.empty()) {
         helpers::load_levels(env_val);
     }
diff --git include/spdlog/details/registry.h include/spdlog/details/registry.h
index 56a6886e..9f08fe47 100644
--- include/spdlog/details/registry.h
+++ include/spdlog/details/registry.h
@@ -104,7 +104,7 @@ private:
     std::unordered_map<std::string, std::shared_ptr<logger>> loggers_;
     log_levels log_levels_;
     std::unique_ptr<formatter> formatter_;
-    spdlog::level::level_enum global_log_level_ = level::info;
+    spdlog::level::level_enum global_log_level_ = level::off;  // compatible with env_logger in Rust
     level::level_enum flush_level_ = level::off;
     err_handler err_handler_;
     std::shared_ptr<thread_pool> tp_;