file extensions

file extensions with names which contain two or more points are not handled correctly (e.g.) tar.gz
e.g. existing file with name foo.tar.gz, new file with same same turn into foo.tar_1.gz and not foo_1.tar.gz

(from redmine: issue id 2012, created on 2014-12-11 by Daniel.Van.Asseldonk, closed on 2015-09-18)