Matching on directories for vim's autocmd

Generally, vim users use the autocmd command to set specific options for filetypes. Like, if you want all Ruby files to have the shiftwidth option set to 2 then you would include an autocmd line like this in your ~/.vimrc file:

autocmd BufRead *.rb set shiftwidth=2

I wanted to do something a bit different. I wanted to set the color scheme for each file in a directory rather than for a file type, and I tried this:

autocmd BufRead *writing* color shine

Nothing happened.

Via :help autocmd-patterns I was able to learn that if there isn't a slash char (/) anywhere in the pattern then it just tries to match on the filename. If a slash is included however, the whole path for that file is matched. All I needed was to add a slash:

autocmd BufRead */writing* color shine

Shine On.