Nix Release 2.5 (2021-12-13) - Key Improvements and New Features

doc/manual/source/release-notes/rl-2.5.md

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# Release 2.5 (2021-12-13)

* The garbage collector no longer blocks new builds, so the message
  `waiting for the big garbage collector lock...` is a thing of the
  past.

* Binary cache stores now have a setting `compression-level`.

* `nix develop` now has a flag `--unpack` to run `unpackPhase`.

* Lists can now be compared lexicographically using the `<` operator.

* New built-in function: `builtins.groupBy`, with the same functionality as
  Nixpkgs' `lib.groupBy`, but faster.

* `nix repl` now has a `:log` command.

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Title: Nix Release 2.5 (2021-12-13) - Key Improvements and New Features

Summary

This release of Nix includes several enhancements such as a garbage collector that no longer blocks new builds, a compression-level setting for binary cache stores, a --unpack flag for `nix develop`, lexicographical list comparison using the `<` operator, a new built-in function `builtins.groupBy`, and a `:log` command for `nix repl`.