### Description In our workflow we require everyone to merge master to their branches before submitting a MR. From the current Merge Request UI page it is not possible to figure out if a branch is behind master or not. This is only shown **after** someone creates the MR. This inofrmation is already available under the *branches* tab but I usually don't use that page to create the MR ### Proposal Display the number of commits behind the target branch while creating the MR in the MR page. ### Feature checklist Make sure these are completed before closing the issue, with a link to the relevant commit. - [ ] [Feature assurance](https://about.gitlab.com/handbook/product/#feature-assurance) - [ ] Documentation - [ ] Added to [features.yml](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/data/features.yml)