Request: More flexible checking?

[kendonB]

As far as I can tell, the current checking options do the following:

• exists checks the target exists and builds if not
• code is exists + checks the target generating code and builds if it changed
• depends is exists + checks ALL the target's dependencies with md5's and builds if one or more has changed

I have a target where a bunch of the dependencies are raw data that will never change, but two dependencies come from earlier code that might change. Computing the md5's on the raw data is expensive, but that seems like the only way to get remake to check the two earlier-code-dependent dependencies.

Perhaps adding check: specific_dependency_name to the API could work? Or is there a way to do this now?

Hope this helps. Great package!