FEATURE REQ: Add option --dry-run to 'add'

[Jari Aalto]

Use case:

    You're about to import 200 files with subdirectories
    You think, you have configured ./.bzrignore correctly
    ... but you have doubts that after 'add' it imports
    ... files that you don't want

You stare the prompt:

    $ bzr add *

And you've no courage to press that red-red-hot RETURN key....
I wish there were --dry-run option.

Jari