My comment might be a bit unclear. Example:
```vim
" Set highlighting for specific files
au BufRead,BufNewFile *.ru set filetype=ruby
au BufRead,BufNewFile *.md set filetype=markdown
```
This way in the future we can just add something like:
```vim
au BufRead,BufNewFile *.jbuilder set filetype=ruby
```
To this group without needing its own specific comment.