"Default dir" option for config command-line script

[Allan LeSage]

The default directory for the command-line script should fall through to the default provided by adt-run itself. I found myself having to mkdir--also note that there's some danger in specifying none or an existing dir as its contents (or root) will be blown away.

[Selene ToyKeeper (toykeeper)]

I think perhaps we might need a separate bug for "adt-run eats small children and its log dir on every execution". It really should work with a log dir of /tmp or . or $HOME, but these obvious choices produce somewhat disastrous results.

[Selene ToyKeeper (toykeeper)]

That's now bug 1463561.

[Brendan Donegan (brendan-donegan)]

ubuntu-system-tests just passed the value of output_dir to adt-run so whatever disastrous consequences there are, are entirely down to adt-run. At most, we could improve the help message to warn about this.