Added detection of XML-derived file types by peeking the file contents

src/source.cpp

@@ -14,6 +14,7 @@
 #include <boost/spirit/home/qi/char.hpp>
 #include <boost/spirit/home/qi/operator.hpp>
 #include <boost/spirit/home/qi/string.hpp>
+#include <fstream>
 #include <iostream>
 #include <limits>
 #include <map>
@@ -88,6 +89,14 @@ Glib::RefPtr<Gsv::Language> Source::guess_language(const boost::filesystem::path
         }
       }
     }
+    else {
+      std::ifstream input(file_path.string(), std::ios::binary);
+      std::string tag(5, '\0');
+      if(input && input.read(&tag[0], static_cast<std::streamsize>(tag.size()))) {
+        if(tag == "<?xml")
+          language = language_manager->get_language("xml");
+      }
+    }
   }
   else if(language->get_id() == "cuda") {
     if(file_path.extension() == ".cuh")