spdlog.patch

diff --git include/spdlog/cfg/env.h include/spdlog/cfg/env.h
index 1f39ebbb..87e3a5f7 100644
--- include/spdlog/cfg/env.h
+++ include/spdlog/cfg/env.h
@@ -25,9 +25,9 @@
 
 namespace spdlog {
 namespace cfg {
-inline void load_env_levels()
+inline void load_env_levels(const char *env_var = "SPDLOG_LEVEL")
 {
-    auto env_val = details::os::getenv("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 b069c3f5..f0e25abe 100644
--- include/spdlog/details/registry.h
+++ include/spdlog/details/registry.h
@@ -97,7 +97,7 @@ 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;
     void (*err_handler_)(const std::string &msg) = nullptr;
     std::shared_ptr<thread_pool> tp_;