Possible resolve to #2

Actually I'm already changing the directory for the duration of several commands, as `make` and `Ack` (which internally uses vim `grep` by changing `grepprg`). The second `autocmd` you suggested is correct, although I don't miss it due to another autocmd that I use ("Set working directory to the file you're editing" - `autocmd BufEnter * lcd %:p:h`). And without it it is possible to check which directory was used by the command with `:pw` on quickfix window.

I'm wanting to avoid that directory change for a few times. As I'm working on very large project, sometimes I need to perform an `Ack` on the current directory, far down the project root.