This is an opam repository that contains beta releases of the OCaml compiler. It is in a separate opam remote from the stable opam-repository so that the beta compilers are an opt-in for advanced users.
To activate this repository in your current opam switch:
opam repo add beta https://github.com/ocaml/ocaml-beta-repository.git
This will add the beta remote as a non-default extra source of opam
packages. You can then create a compiler switch to the trunk compiler
by:
opam switch create 408 ocaml-variants.4.08.0+trunk --repositories=default,beta
This will create the 408 switch and make the opam packages from the
default opam repository available, but compiled with the beta version
of the compiler.