feat(3p/nixpkgs): Expose nixpkgs commit hashes r/2720

This makes it possible to use the hashes in things that should, for
example, be keyed on the nixpkgs version (such as cache-folders for
Nixery).

Change-Id: I500d13a4d96b0c28fcf6ca383d2a86515565da36
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3341
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/third_party/nixpkgs/default.nix b/third_party/nixpkgs/default.nix
index fa42b5bb7b..eb3c1ca86c 100644
--- a/third_party/nixpkgs/default.nix
+++ b/third_party/nixpkgs/default.nix
@@ -49,10 +49,19 @@ let
   stableOverlay = self: super: {
     # nothing picked from stable currently
   };
+
+  # Overlay to expose the nixpkgs commits we are using to other Nix code.
+  commitsOverlay = _: _: {
+    nixpkgsCommits = {
+      unstable = unstableHashes.commit;
+      stable = stableHashes.commit;
+    };
+  };
 in import nixpkgsSrc {
   config.allowUnfree = true;
   config.allowBroken = true;
   overlays = [
+    commitsOverlay
     stableOverlay
     depot.third_party.overlays.tvl
     depot.third_party.overlays.haskell