explain the idea begind tracking/parents/inheriting defines

[maddanio]

I am hacking around in cget to get it to work for us, and I am confused by the tracking concept, and dependency files in the packages. they contain the name of the package with one letter per line :).
Also why do dependencies when built because of another package inherit that packages defines?

1. they often dont make sense for this (i.e. when I configure the cmake build with defines that doesnt have any meaning for its dependents)
2. packages are now built differently dependening on how they where discovered to be required

the latter btw is already kinda true because of variants, so that probably has to be thought over. i.e. if I install xz release, then opencv with debug xz is built release. but if the order is reversed xz is built debug.