The Nix CLI now searches for a flake.nix up until the root of the current
Git repository or a filesystem boundary rather than just in the current
directory.
The TOML parser used by builtins.fromTOML has been replaced by a
more compliant one.
Added :st/:show-trace commands to nix repl, which are used to
set or toggle display of error traces.
New builtin function builtins.zipAttrsWith with the same
functionality as lib.zipAttrsWith from Nixpkgs, but much more
efficient.
New command nix store copy-log to copy build logs from one store
to another.
The commit-lockfile-summary option can be set to a non-empty
string to override the commit summary used when commiting an updated
lockfile. This may be used in conjunction with the nixConfig
attribute in flake.nix to better conform to repository
conventions.
docker run -ti nixos/nix:master will place you in the Docker
container with the latest version of Nix from the master branch.