Release 0.7.0

Added

• Define rules_nixpkgs_dependencies in //nixpkgs:repositories.bzl.
• Define nixpkgs_go_configure in //nixpkgs:toolchains/go.bzl
• nixpkgs_package now has a quiet attribute.

Changed

• The constraint value for targets to detect whether Nix is available
  on the current platform is now called
  @//nixpkgs/constraints:support_nix. The associated constraint
  setting is @//nixpkgs/constraints:nix. The old constraint
  @//nixpkgs/constraints:nixpkgs constraint setting is still
  available. But it is highly recommended to migrate to the new
  constraint setting, and update platform definitions accordingly.
  This is a breaking change for users of nixpkgs_python_configure.
• Show Nix output by default, like in releases prior to v0.6.

Fixed

• nixpkgs_local_repository now correctly invalidates the cache when
  Nix source files change. See
  #123.