Actually, I've often thought that this conditional is unnecessary: Always match for the regex, and if it's empty, it works anyway. To test this, I reduced the code to:
```ruby
Dir.glob(File.join(@site.dest, "**", "*"), File::FNM_DOTMATCH) do |file|
  files << file unless file =~ /\/\.{1,2}$/ || file =~ keep_file_regex
end
```
All tests still pass. So unless this is due to a missing test, I'll remove the condition.