# File lib/rake/ext/string.rb, line 13
13:     def ext(newext='')
14:       return self.dup if ['.', '..'].include? self
15:       if newext != ''
16:         newext = (newext =~ /^\./) ? newext : ("." + newext)
17:       end
18:       self.chomp(File.extname(self)) << newext
19:     end