- To RuboCop the current commit
```
git diff-tree --no-commit-id --name-only -r HEAD --diff-filter AMT | xargs bundle exec rubocop
```
- To RuboCop the working tree changes
```
git diff --name-only --diff-filter AMT | xargs bundle exec rubocop
```
- To RuboCop all of the changes from the branch
```
git diff --name-only master --diff-filter AMT | xargs bundle exec rubocop
```
From https://about.gitlab.com/handbook/tools-and-tips/rubocop/
Also see:
- https://github.com/danger/danger
- https://github.com/danger/awesome-danger
- https://github.com/prontolabs/pronto
- https://github.com/prontolabs/pronto#runners
- https://github.com/danger/danger-gitlab-gem