Add several new functions to the C API:
StorePath operations:
- nix_store_path_hash: Extract the hash part from a store path
- nix_store_create_from_parts: Construct a store path from hash and name
Derivation operations:
- nix_derivation_clone: Clone a derivation
- nix_derivation_to_json: Serialize a derivation to JSON
Store operations:
- nix_store_drv_from_store_path: Load a derivation from a store path
Test the new functions, and improve documentation of some existing
functions to better distinguish them, also.
Co-authored-by: Tristan Ross <tristan.ross@determinate.systems>
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Move StorePath and Derivation declarations to their own headers in a
backwards compatible way:
- Created nix_api_store/store_path.h for StorePath operations
- Created nix_api_store/derivation.h for Derivation operations
- Main nix_api_store.h includes both headers for backwards compatibility
This reorganization improves modularity and hopefully makes the API
easier to navigate.
They are not actually part of the store layer, but instead part of the
Nix executable infra (libraries don't need plugins, executables do).
This is part of a larger project of moving all of our legacy settings
infra to libmain, and having the underlying libraries just have plain
configuration structs detached from any settings infra / UI layer.
Progress on #5638
See https://github.com/NixOS/nix/pull/8699#discussion_r1554312181
Casting a function pointer to `void*` is undefined behavior in the C
spec, since there are platforms with different sizes for these two kinds
of pointers. A safe alternative might be `void (*callback)()`
