Ruby's equivalent should use the :path parameter when specifying a gem in your Gemfile. It will look something like this.
gem "mylocalgem", :path => "/path/to/local/gem/dir/"
If you are trying to do this globally by default ruby โโof the system, you can do one of the following.
gem install
or just run the following from the directory where the .gem file exists and it will be raised.
gem install
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