ultimate-vim/sources_non_forked/nginx-vim-syntax/ftdetect/nginx.vim

au BufRead,BufNewFile *.nginx set ft=nginx
au BufRead,BufNewFile */etc/nginx/* set ft=nginx
au BufRead,BufNewFile */usr/local/nginx/conf/* set ft=nginx
au BufRead,BufNewFile nginx.conf set ft=nginx