From ec91266fcd12f16d8ca355ab70a14f2b4c2c4691 Mon Sep 17 00:00:00 2001
From: Wroclaw <wroclaw223@outlook.com>
Date: Sun, 9 Feb 2025 08:23:49 +0100
Subject: [PATCH] pkgs/overlays/unstable-latest: init

this reuses code that was removed in 77ef7434f24baa95c6929a9e532967b0e58b7294
---
 pkgs/overlays/unstable-from-source.nix |  3 ++-
 pkgs/overlays/unstable-latest.nix      | 25 +++++++++++++++++++++++++
 pkgs/top-level/default.nix             |  1 +
 3 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 pkgs/overlays/unstable-latest.nix

diff --git a/pkgs/overlays/unstable-from-source.nix b/pkgs/overlays/unstable-from-source.nix
index 214307d..9f9499c 100644
--- a/pkgs/overlays/unstable-from-source.nix
+++ b/pkgs/overlays/unstable-from-source.nix
@@ -1,5 +1,6 @@
 {
   unstableSource,
+  attributeName ? "unstable",
 }:
 
 self: super:
@@ -32,5 +33,5 @@ let
   });
 in
 {
-  unstable = if useUnstable then unstablePkgsForNixpkgs self else self;
+  "${attributeName}" = if useUnstable then unstablePkgsForNixpkgs self else self;
 }
diff --git a/pkgs/overlays/unstable-latest.nix b/pkgs/overlays/unstable-latest.nix
new file mode 100644
index 0000000..68636c0
--- /dev/null
+++ b/pkgs/overlays/unstable-latest.nix
@@ -0,0 +1,25 @@
+self: super:
+
+let
+  nixos = self.config.unstable-latest.nixos or true;
+  useUnstable = self.config.useUnstable or true;
+
+  unstablePkgsExprs = if nixos
+      then builtins.fetchTarball "https://channels.nixos.org/nixos-unstable/nixexprs.tar.xz"
+      else builtins.fetchTarball "https://channels.nixos.org/nixpkgs-unstable/nixexprs.tar.xz";
+
+  # Compiled nixpkgs expression eg expressions from a nix channel
+  nixpkgsVersion = builtins.concatStringsSep "." [
+    (builtins.readFile "${unstablePkgsExprs}/.version")
+    (builtins.readFile "${unstablePkgsExprs}/.version-suffix")
+  ];
+
+  nixpkgsRevision = (builtins.readFile "${unstablePkgsExprs}/.git-revision");
+in
+import ./unstable-from-source.nix {
+  unstableSource = unstablePkgsExprs;
+  attributeName = "unstable-latest";
+} self super // {
+  unstableLatestVersion = if !useUnstable then null else nixpkgsVersion;
+  unstableLatestRevision = if !useUnstable then null else nixpkgsRevision;
+}
diff --git a/pkgs/top-level/default.nix b/pkgs/top-level/default.nix
index dfdae8b..34637da 100644
--- a/pkgs/top-level/default.nix
+++ b/pkgs/top-level/default.nix
@@ -15,6 +15,7 @@ let
       # ../.. should be nix store path that represents self in outputs.nix that is gc-rooted by this point
       ( import ../overlays/selfExpr.nix { nixpkgsPath = "${builtins.toString ../..}/pkgs/top-level/impure.nix"; } )
       ( import ../overlays/unstable-with-meta.nix { unstableSource = inputs.nixpkgs-unstable; revision = inputs.lock.nixpkgs-unstable.revision; } )
+      ( import ../overlays/unstable-latest.nix )
       ( import ../overlays/version-info-fixup.nix { inherit inputs; } )
       ( import ./by-name-overlay.nix ../by-name )
     ];