Release X.Y (202?-??-??)

Nix now provides better integration with zsh's run-help feature. It is now included in the Nix installation in the form of an autoloadable shell function, run-help-nix. It picks up Nix subcommands from the currently typed in command and directs the user to the associated man pages.
nix repl has a new build-'n-link (:bl) command that builds a derivation while creating GC root symlinks.
The path produced by builtins.toFile is now allowed to be imported or read even with restricted evaluation. Note that this will not work with a read-only store.
nix build has a new --print-out-paths flag to print the resulting output paths. This matches the default behaviour of nix-build.
Nix can now be built with LTO by passing --enable-lto to configure. LTO is currently only supported when building with GCC.
You can now specify which outputs of a derivation nix should operate on using the syntax installable^outputs, e.g. nixpkgs#glibc^dev,static or nixpkgs#glibc^*. By default, nix will use the outputs specified by the derivation's meta.outputsToInstall attribute if it exists, or all outputs otherwise.

Selecting derivation outputs using the attribute selection syntax (e.g. nixpkgs#glibc.dev) no longer works.