*sh: teach `ds` to do something without args
*sh: teach `ds` to do something without args

Previously, `ds` without args would do nothing and `ds --watch` without
args would complain.

Now, both will assume you want to update/watch dirty projects. If you
don't specify any projects and there aren't any dirty projects, `ds
--watch` will complain, because it doesn't know what to do.

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent