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-Tvix, also known as TVL's fork of Nix
--------------------------------------
-
-Nix is a new take on package management that is fairly unique. Because
-of its purity aspects, a lot of issues found in traditional package
-managers don't appear with Nix.
-
-To find out more about the tool, usage and installation instructions,
-please read the manual, which is available on the Nix website at
-<http://nixos.org/nix/manual>.
-
-This repository is [TVL's](https://tvl.fyi)'s fork of Nix, which we lovingly
-refer to as Tvix.
-
-## Fork background
-
-Nix is a fantastic project with over a decade of demonstrated
-real-world usage, but also with quite a few problems.
-
-First of all, the project consists of two main components: The Nix
-package collection ("[nixpkgs][]") and the package manager itself.
-
-The package collection is an enormous effort with hundreds of
-thousands of commits, encoding expert knowledge about lots of
-different software and ways of building and managing it. It is a very
-valuable piece of software.
-
-The package manager however is an old C++ project with severe code
-quality issues, little to no documentation, no consistent style and no
-unit test coverage.
-
-Its codebase is larger than it needs to be (often due to custom
-reimplementations of basic functionality) and is mostly ad-hoc
-structured, making it difficult to correctly implement large-scale
-improvements.
-
-In addition, the upstream Nix project is diverging from the opinions
-of some community members via the introduction of concepts such as Nix
-flakes.
-
-To counteract these things we have decided to fork Nix.
-
-## Fork goals
-
-The things listed here are explicitly in-scope for work on the fork.
-This list is not exhaustive, and it is very likely that many other
-smaller things will be discovered along the way.
-
-### nixpkgs compatibility
-
-This fork will maintain compatibility with nixpkgs as much as
-possible. If at any point we do need to diverge, we will do it in a
-way that is backwards compatible.
-
-### Code quality improvements
-
-Code quality encompasses several different issues.
-
-One goal is to slowly bring the codebase in line with the [Google C++
-style guide][google-style]. Apart from the trivial reformatting (which
-is already done), this means slowly chipping away at incorrectly
-structured type hierarchies, usage of exceptions, usage of raw
-pointers, global mutability and so on.
-
-Another goal is to reduce the amount of code in Nix by removing custom
-reimplementations of basic functionality (such as string splitting or
-reading files).
-
-For functionality that is not part of the C++17 standard library,
-[Abseil][] will be the primary external library used.
-
-### Explicit RPC mechanisms
-
-Nix currently uses homegrown mechanisms of interacting with other Nix
-binaries, for example for remote builds or interaction between the CLI
-and the Nix daemon.
-
-This will be replaced with [gRPC][].
-
-### New sandboxing mechanism
-
-Nix implements its own sandboxing mechanism. This was probably the
-correct decision at the time, but is not necessary anymore because
-Linux containers have become massively popular and lots of new tooling
-is now available.
-
-The goal is to replace the custom sandboxing implementation with
-pluggable [OCI runtimes][oci], which will make it possible to use
-arbitrary container runtimes such as [gVisor][] or [systemd-nspawn][]
-
-### Pluggable Nix store backends
-
-The current Nix store implementation will be removed from Nix' core
-and instead be refactored into a gRPC API that can be implemented by
-different backends.
-
-### Builds as graph reductions
-
-A Nix derivation that should be instantiated describes a build graph.
-This graph will become a first-class citizen, making it possible to
-distribute different parts of the computation to different nodes.
-
-Implementing this properly will also allow us to improve the
-implementation of import-from-derivation by explicitly moving through
-different graph reduction stages.
-
-## Fork non-goals
-
-To set expectations, there are some explicit non-goals, too.
-
-* Merging these changes back into upstream is not a goal, and maybe
-  not even feasible. The core work has not even started yet and just
-  basic cleanup has already created a diff of over 40 000 lines.
-
-  This would likely also turn into a political effort, which we have
-  no interest in.
-
-* Improved performance is not an (initial) goal. Nix performance is
-  very unevenly distributed across the codebase (some things have seen
-  a lot of ad-hoc optimisation, others are written like inefficient
-  toy implementations) and we simply don't know what effect the
-  cleanup will have.
-
-  Once the codebase is in a better state we will be able to start
-  optimising it again while retaining readability, but this is not a
-  goal until a later point in time.
-
-* Compatibility with new upstream features is not a goal. Specifically
-  we do not want Nix flakes, but other changes upstream makes will be
-  considered for inclusion.
-
-* Support for non-Linux systems. Currently Nix support Mac OS and
-  potentially other systems, but this support will be dropped.
-
-  Once we have OCI-compatible sandboxes and a store protocol it will
-  be possible to reintroduce these with less friction.
-
-## Building
-
-To build the project, set up an out-of-tree cmake directory and run cmake in
-nix-shell.
-
-```
-mkdir ~/build/tvix
-cd ~/build/tvix
-
-nix-shell $DEPOT_PATH -A third_party.nix.build-shell
-
-# Disable clang-tidy for quicker builds
-cmake $DEPOT_PATH/third_party/nix/ -DCLANG_TIDY_PATH=""
-make -j16 -l12
-
-# Run tests
-make test
-```
-
-## Contributing to the fork
-
-The TVL depot's default [contribution guidelines][contributing] apply.
-
-In addition, please make sure that submitted code builds and is
-formatted with `clang-format`, using the configuration found in this
-folder.
-
-## License
-
-Nix is released under the LGPL v2.1
-
-This product includes software developed by the OpenSSL Project for
-use in the [OpenSSL Toolkit](http://www.OpenSSL.org/).
-
-[nixpkgs]: https://github.com/NixOS/nixpkgs
-[google-style]: https://google.github.io/styleguide/cppguide.html
-[Abseil]: https://abseil.io/
-[gRPC]: https://grpc.io/
-[oci]: https://www.opencontainers.org/
-[gVisor]: https://gvisor.dev/
-[systemd-nspawn]: https://www.freedesktop.org/software/systemd/man/systemd-nspawn.html
-[contributing]: https://cs.tvl.fyi/depot/-/blob/docs/CONTRIBUTING.md