format: add specifier detection for fs::path

format.hpp

@@ -23,7 +23,8 @@
 namespace util {
     namespace format {
         template <typename ...Args>
-        std::string render (const std::string &fmt, Args&&...);
+        std::string
+        render (const std::string &fmt, Args&&...);
 
         class error : public std::runtime_error
         { using runtime_error::runtime_error; };

format.ipp

@@ -25,6 +25,7 @@
 #include <sstream>
 #include <stdexcept>
 #include <iterator>
+#include <boost/filesystem/path.hpp>
 
 namespace util {
     namespace detail { namespace format {
@@ -41,6 +42,7 @@ namespace util {
         is_valid_specifier<const char*> (const char *s)
         { return *s == 's'; }
 
+
         //---------------------------------------------------------------------
         template <>
         inline bool
@@ -55,6 +57,13 @@ namespace util {
         { return *s == 's'; }
 
 
+        //---------------------------------------------------------------------
+        template <>
+        inline bool
+        is_valid_specifier<boost::filesystem::path> (const char *s)
+        { return *s == 's'; }
+
+
         //---------------------------------------------------------------------
         template <>
         inline bool