[0002] Add autoCall helper function to package sets

[jonringer]

Provide something similar to callPackage, but allows for just passing arguments from a package scope to a function with out calling mkOverridable which adds .override and .overrideDerivation continuation functions.

[blaggacao]

Personally, I would have wished multiple times in the past that derivation attributes were bound to a complete specification.

While providing ample flexibility to the first user, the lack of bounds communicates uncertainty and lack of stability to the second and beyond.

It also limits the maintainability and elegance of "metaprogramming" approaches over the output attribute set, because their schema must be assumed to be inherently unstable.

With that experience and intuition, I'd even posit to locking down output attributes to a clear and stable, and if need be versioned, specification, with a special, "untyped/freeform" attribute to host any remaining need for flexibility, but used with restraint in tier one eka repositories.

Pseudo "code study":

drv.v1.*  # v1 specced
drv.v2.*  # v2 specced
drv.any.*  # freeform, use with restraint!