Code review comment for lp:~broder/ubuntu-dev-tools/backportpackage

I'm with you on the current directory thing. But I'm also hesitant about adding a 3rd behavior.

I guess that as this generates something the user isn't expecting to work with, /tmp is correct. But then I think we should give mkdtemp a 'backportpackage' prefix (so it can be easily tab-completed) and document the fact that it'll build in /tmp in the manpage.