Merge branch 'rs-prepare-for-absorb' into 'master'

.rubocop.yml

.rubocop_todo.yml

Gemfile

Guardfile

gemfiles/rails_42.gemfile

gemfiles/rails_50.gemfile

lib/gitlab_git/blame.rb

lib/gitlab_git/blob.rb

lib/gitlab_git/commit.rb

lib/gitlab_git/diff_collection.rb

lib/gitlab_git/repository.rb

lib/gitlab_git/tag.rb

performance/Rakefile

performance/test/load_large_diff.rb

spec/blob_spec.rb

spec/commit_spec.rb

spec/diff_collection_spec.rb

spec/diff_spec.rb

spec/repository_spec.rb

spec/spec_helper.rb