Moved namespace fmt to be under spdlog::details to minimize namespace pollution for the users

include/spdlog/details/format.h

@@ -115,7 +115,8 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define FMT_DISALLOW_COPY_AND_ASSIGN(TypeName) \
   TypeName(const TypeName&); \
   void operator=(const TypeName&)
-
+namespace spdlog {
+namespace details {
 namespace fmt
 {
 
@@ -2739,7 +2740,9 @@ inline void format_decimal(char *&buffer, T value)
     internal::format_decimal(buffer, abs_value, num_digits);
     buffer += num_digits;
 }
-}
+} // ns fmt
+} // ns deatils
+} // ns spdlog
 
 #if FMT_GCC_VERSION
 // Use the system_header pragma to suppress warnings about variadic macros
@@ -2846,6 +2849,8 @@ fmt::print(format, args...);
 #define FMT_VARIADIC_W(ReturnType, func, ...) \
   FMT_VARIADIC_(wchar_t, ReturnType, func, return func, __VA_ARGS__)
 
+namespace spdlog {
+namespace details {
 namespace fmt
 {
 FMT_VARIADIC(std::string, format, StringRef)
@@ -2858,6 +2863,8 @@ FMT_VARIADIC(std::string, sprintf, StringRef)
 FMT_VARIADIC(int, printf, StringRef)
 FMT_VARIADIC(int, fprintf, std::FILE *, StringRef)
 }
+}
+}
 
 // Restore warnings.
 #if FMT_GCC_VERSION >= 406

include/spdlog/details/pattern_formatter_impl.h

@@ -582,8 +582,8 @@ inline void spdlog::pattern_formatter::format(details::log_msg& msg)
         //write eol
         msg.formatted << details::os::eol();
     }
-    catch(const fmt::FormatError& e)
+    catch(const details::fmt::FormatError& e)
     {
-        throw spdlog_ex(fmt::format("formatting error while processing format string: {}", e.what()));
+        throw spdlog_ex(details::fmt::format("formatting error while processing format string: {}", e.what()));
     }
 }

include/spdlog/sinks/file_sinks.h

@@ -99,7 +99,7 @@ protected:
 private:
     static std::string calc_filename(const std::string& filename, std::size_t index, const std::string& extension)
     {
-        fmt::MemoryWriter w;
+        details::fmt::MemoryWriter w;
         if (index)
             w.write("{}.{}.{}", filename, index, extension);
         else
@@ -196,7 +196,7 @@ private:
     static std::string calc_filename(const std::string& basename, const std::string& extension)
     {
         std::tm tm = spdlog::details::os::localtime();
-        fmt::MemoryWriter w;
+        details::fmt::MemoryWriter w;
         w.write("{}.{:04d}-{:02d}-{:02d}.{}", basename, tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, extension);
         return w.str();
     }