Horizon.Config.Pretty

A local package as its pkgs/*.nix names it: its directory and the .cabal the file was rendered from, each a Nix path literal relative to the file, and that .cabal's sha256.

Render a derivation with, for a local package, its source, and the source patches to apply, each a Nix path literal relative to the file the derivation is written to. The patches are the generic builder's patches, exactly what haskell.lib.appendPatches would set, so the file stays a plain function of its dependencies. A local package's src is its directory, a path the evaluator reads, never a derivation it must build first; the set it is called in decides what of the directory is source. Its passthru records the .cabal it was rendered from and that file's sha256, so evaluation alone can tell whether the file is current.