refactor(tvix/nix-compat): absorb nar writer

Expose it at `nix_compat::nar::writer`.

Change-Id: I98a8acfa6277074f24608d64fb6c0082b41d10f5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7969
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/Cargo.lock

@@ -2675,10 +2675,6 @@ dependencies = [
  "tvix-eval",
 ]
 
-[[package]]
-name = "tvix-nar"
-version = "0.0.0"
-
 [[package]]
 name = "tvix-serde"
 version = "0.1.0"

tvix/Cargo.toml

@@ -21,7 +21,6 @@ members = [
   "cli",
   "eval",
   "eval/builtin-macros",
-  "nar",
   "nix_cli",
   "nix-compat",
   "serde",

tvix/nar/Cargo.toml

@@ -1,4 +0,0 @@
-[package]
-name = "tvix-nar"
-version = "0.0.0"
-edition = "2021"

tvix/nar/default.nix

@@ -1,5 +0,0 @@
-{ depot, ... }:
-
-depot.tvix.crates.workspaceMembers.tvix-nar.build.override {
-  runTests = true;
-}

tvix/nix-compat/src/lib.rs

@@ -1,3 +1,4 @@
 pub mod derivation;
+pub mod nar;
 pub mod nixbase32;
 pub mod store_path;

tvix/nix-compat/src/nar/mod.rs

@@ -0,0 +1 @@
+pub mod writer;

tvix/nix-compat/src/nar/writer/mod.rs

@@ -16,7 +16,7 @@
 //! let mut sink: Vec<u8> = Vec::new();
 //!
 //! // Instantiate writer for this output location.
-//! let mut nar = tvix_nar::open(&mut sink)?;
+//! let mut nar = nix_compat::nar::writer::open(&mut sink)?;
 //!
 //! // Acquire metadata for the single file to output, and pass it in a
 //! // `BufRead`-implementing type.