* Added descriptors for gtkspell and its support package pspell.
Gtkspell is an optional dependency of Pan, so we should add the
ability to nix-instantiate to instantiate variants of a package
based on a selection of features.
action. Run actions are described by uniquely hashed descriptors,
just like build actions. Therefore run actions can have
dependencies, but these need not be the same as the build time
dependencies (e.g., at runtime we can link against a different
version of a dynamic library). Example:
nix run 31d6bf4c171282367065e0deecd7c579
will run the Pan 0.13.91 newsreader with gtkspell support.
descriptor templates under the import relation. I.e., we can now
say:
nix-instantiate outdir foo.nix
which will create descriptors for foo.nix and all imported packages
in outdir/.
files) are now referenced using their cryptographic hashes.
This ensures that if two package descriptors have the same contents,
then they describe the same package. This property is not as
trivial as it sounds: generally import relations cause this property
not to hold w.r.t. temporality. But since imports also use hashes
to reference other packages, equality follows by induction.
Eelco Dolstra