Release 3.12.2 (2025-11-05)

What's Changed

Faster revCount computation

When using Git repositories with a long history, calculating the revCount attribute can take a long time. Determinate Nix now computes revCount using multiple threads, making it much faster.

Note that if you don't need revCount, you can disable it altogether by setting the flake input attribute shallow = false.

PR: DeterminateSystems/nix-src#245

More readable error messages

Previously, Nix showed full flakerefs in error messages such as stack traces, e.g.

   … from call site
     at «github:NixOS/nixpkgs/3bea86e918d8b54aa49780505d2d4cd9261413be?narHash=sha256-Ica%2B%2BSXFuLyxX9Q7YxhfZulUif6/gwM8AEQYlUxqSgE%3D»/lib/customisation.nix:69:16:
       68|     let
       69|       result = f origArgs;
         |                ^
       70|

It now abbreviates these by leaving out narHash and shortening Git revisions:

   … from call site
     at «github:NixOS/nixpkgs/3bea86e»/lib/customisation.nix:69:16:
       68|     let
       69|       result = f origArgs;
         |                ^
       70|

PR: DeterminateSystems/nix-src#243

Other changes

This release fixes an assertion failure in nix flake check. PR: DeterminateSystems/nix-src#252

Full Changelog: v3.12.1...v3.12.2