subversion (svn) E205007 (commit failed). could not use external editor to fetch log message

You need to include a message when you commit. Use the command svn ci filename.xml -m "your message here". The message is a descriptor of what you are adding, and/or why you are adding it.

Check this out: Why cant I use the $SVN_EDITOR environment variable in cygwin?. You have to set a default editor for SVN, but just exporting EDITOR might do it.