Index: app/controllers/repositories_controller.rb
===================================================================
--- app/controllers/repositories_controller.rb	(revision 2821)
+++ app/controllers/repositories_controller.rb	(working copy)
@@ -119,7 +119,14 @@
     show_error_not_found and return unless @content
     if 'raw' == params[:format] || @content.is_binary_data? || (@entry.size && @entry.size > Setting.file_max_size_displayed.to_i.kilobyte)
       # Force the download
-      send_data @content, :filename => @path.split('/').last
+      fn = @path.split('/').last
+      type = Redmine::MimeType.of(fn) #Get the Mime-Type of the File
+      if type
+        send_data @content, :filename => fn, :type => type, :disposition => 'inline'
+      else
+        send_data @content, :filename => fn
+      end
+
     else
       # Prevent empty lines when displaying a file with Windows style eol
       @content.gsub!("\r\n", "\n")