Add --no-run args to depends which checks artifacts but does not run the task

[cassaundra]

Useful for install tasks which depend on an up-to-date dist but do not want to necessarily invoke the task if it is dirty (e.g. quake bundle-dist && sudo quake install-dist.

Implementation

Add --no-run flag that, when running dirty checks on the dependee, an error is emitted instead of running the task. For dependees with no possible dirty check mechanism (at the moment just having sources and artifacts), we should make this error include a suggestion to add such a mechanism.