The createTask(...) api in Gradle creates what amounts to a .PHONY target in Gnu Make.
That's very useful but so are non .PHONY targets, such as file names.

It would also be nice if there were a nice syntax for specifying how the dependsOn relationship
for a file target is evaluated. The two obvious methods are time stamp (like Make and most others)
and some sort of crypto hash such as MD5 or SHA1 (like Scons and Rant).

For more information on 'Rant', see: http://rant.rubyforge.org/
For more information on Scons, see: http://www.scons.org/

You could also imagine how there could be a need to plug in an arbitrary function,
so it would be great if Gradle could do that too.

The benefit of MD5 over time stamps is that it eliminates clock skew problems
(however it is more expensive to evaluate). Thus, an ideal solution would let you
do whatever you wanted globally and/or target-by-target (with the ability to override
a global default).

Obviously, a file task should be allowed to depend on both file and non-file tasks.

It might be worth starting a discussion thread on the mailing list about this
and explore the pros/cons of different syntax proposals.