We have released this version as a release candidate (rc) because it contains fundamental changes to rebar3's package handling. This should be a backwards compatible change for users, but significant internally. Even if you don't make use of the new features, we would like to receive your feedback to ensure nothing has broken for your everyday use.
The main new features in this release:
* Support for hex v2. This is a more efficient registry implementation which is updated per-package only as needed, which should save memory, disk space, and allow for faster start times.
* Support for multiple repository fetching. Repositories are defined as a list and searched sequentially for the first match. This allows the development and overlaying of private indexes and mirrors
* Multiple repos includes private Hex organizations (https://hex.pm/pricing) which are defined the same way as they are for mix users.
Additionally, Elixir packages are no longer filtered from the registry. I'm in the process of updating the plugin, https://github.com/barrel-db/rebar3_elixir_compile, for these changes to provide much smoother support for all mix packages in rebar3 projects.
There will also be an updated resource plugin API to be stabilized soon enough.