Following discussion with Shea and Graham. It's a big enough change
from the last release. Also, from a semver perspective, 2.0 makes more
sense because we did remove some interfaces (like nix-pull/nix-push).

This command upgrades Nix to the latest stable version by installing a
store path obtained from

  https://github.com/NixOS/nixpkgs/raw/master/nixos/modules/installer/tools/nix-fallback-paths.nix

which is the same store path that the installer at
https://nixos.org/nix/install.sh uses.

The upgrade fails if Nix is not installed in a profile (e.g. on NixOS,
or when installed outside of the Nix store).

This didn't support specifying a revision/branch, and was restricted
to git:// URIs (since https:// or ssh:// would be ambiguous).

This allows network access in restricted eval mode.

Accidentally committed this change as part of
f9686885.

Restricted mode != pure mode.

Almost all other primops are camelCase so no reason not to use that
here.

Nix can now automatically run the garbage collector during builds or
while adding paths to the store. The option "min-free = <bytes>"
specifies that Nix should run the garbage collector whenever free
space in the Nix store drops below <bytes>. It will then delete
garbage until "max-free" bytes are available.

Garbage collection during builds is asynchronous; running builds are
not paused and new builds are not blocked. However, there also is a
synchronous GC run prior to the first build/substitution.

Currently, no old GC roots are deleted (as in "nix-collect-garbage
-d").

This removes the file nix-mode.el from Nix. The file is now available within the
repository https://github.com/NixOS/nix-mode.

Fixes #662
Fixes #1040
Fixes #1054
Fixes #1055
Closes #1119
Fixes #1419

NOTE: all of the above should be fixed within NixOS/nix-mode. If one of those
hasn’t please reopen within NixOS/nix-mode and not within NixOS/nix.

(cherry picked from commit c20641ce)

(cherry picked from commit 0fb60e4e)

Looks like this snuck into the 1.11 release notes post-release, but
float support isn't actually present until 1.12.

We set build-cores automatically, not build-max-jobs. (The commit
message for de4cdd0d also got this
wrong.)

- rename options but leav old names as lower-priority aliases,
  also "-dirs" -> "-paths" to get closer to the meaning
- update docs to reflect the new names (old aliases are not documented),
  including a new file with release notes
- tests need an update after corresponding changes to nixpkgs
- __noChroot is left as it is (after discussion on the PR)

So you can now do things like:

  $ nix-env -qa '.*zip.*'
  $ nix-env -qa '.*(firefox|chromium).*'