ruby-core is problematic as it is too big.
It is impossible to fix pkgs dependencies as
ruby-core would generate multiple cycled dependencies
between packages.
Also, "core" in ruby context means "classes that does not need a 'require'".
This is not the case of ruby-core classes. They are, actually, a subset of
Ruby Standard Library.
In every detected case where a portion of ruby-core could be isolated and
save another pkgs from requiring all ruby-core where spin-off into a new
subset. Also, big portions of ruby-core, not require by current ruby-* pkgs
where spin-off in new pkgs. The remaining of ruby-core was put into a new ruby-misc.
ruby-stdlib was created as a meta package that requires all ruby packages that are
part of Ruby Standard Library. For a full Ruby Standard Library, just install
ruby-stdlib and its deps.