Fixed some clang-tidy warning

include/spdlog/details/file_helper.h

@@ -136,7 +136,7 @@ public:
 
         // treat casese like "/etc/rc.d/somelogfile or "/abc/.hiddenfile"
         auto folder_index = fname.rfind(details::os::folder_sep);
-        if (folder_index != fname.npos && folder_index >= ext_index - 1)
+        if (folder_index != filename_t::npos && folder_index >= ext_index - 1)
         {
             return std::make_tuple(fname, spdlog::filename_t());
         }

include/spdlog/details/registry.h

@@ -112,7 +112,7 @@ public:
     void flush_every(std::chrono::seconds interval)
     {
         std::lock_guard<std::mutex> lock(flusher_mutex_);
-        std::function<void()> clbk(std::bind(&registry::flush_all, this));
+        std::function<void()> clbk = std::bind(&registry::flush_all, this);
         periodic_flusher_.reset(new periodic_worker(clbk, interval));
     }