Resync the buffer's idea of the current directory stack.
This command queries the shell with the command bound to
`shell-dirstack-query' (default "dirs"), reads the next
line output and parses it to form the new directory stack.
DON'T issue this command unless the buffer is at a shell prompt.
Also, note that if some other subprocess decides to do output
immediately after the query, its output will be taken as the
new directory stack -- you lose. If this happens, just do the command again. (fn)