This is primarily a bug fix release. It also has a number of new features: A number of builtin functions have been added to reduce Nixpkgs/NixOS evaluation time and memory consumption: all, any, concatStringsSep, foldl’, genList, replaceStrings, sort. The garbage collector is more robust when the disk is full. Nix supports a new API for building derivations that doesn’t require a .drv file to be present on disk; it only requires an in-memory representation of the derivation. This is used by the Hydra continuous build system to make remote builds more efficient. The function <nix/fetchurl.nix> now uses a builtin builder (i.e. it doesn’t require starting an external process; the download is performed by Nix itself). This ensures that derivation paths don’t change when Nix is upgraded, and obviates the need for ugly hacks to support chroot execution. --version -v now prints some configuration information, in particular what compile-time optional features are enabled, and the paths of various directories. Build users have their supplementary groups set correctly. This release has contributions from Eelco Dolstra, Guillaume Maudoux, Iwan Aucamp, Jaka Hudoklin, Kirill Elagin, Ludovic Courtès, Manolis Ragkousis, Nicolas B. Pierron and Shea Levy.