class RuboCop::Cop::Bundler::DuplicatedGem

A Gem’s requirements should be listed only once in a Gemfile.

@example

# bad
gem 'rubocop'
gem 'rubocop'

# bad
group :development do
  gem 'rubocop'
end

group :test do
  gem 'rubocop'
end

# good
group :development, :test do
  gem 'rubocop'
end

# good
gem 'rubocop', groups: [:development, :test]

# good - conditional declaration
if Dir.exist?(local)
  gem 'rubocop', path: local
elsif ENV['RUBOCOP_VERSION'] == 'master'
  gem 'rubocop', git: 'https://github.com/rubocop/rubocop.git'
else
  gem 'rubocop', '~> 0.90.0'
end