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