<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=416700) </details> <!--IssueSummary end--> ### Problem to solve On the MR creation page we only show base comparison of changes from source branch to target branch while on the MR page, we show a straight comparison of changes from source branch to target branch to show how the changes will look like when merged (only if there are no conflicts). This can be confusing to users because of the difference of output. ### Proposal Based on https://gitlab.com/gitlab-org/gitlab/-/issues/371018#note_1450455138: Change the comparison on the MR creation page to: 1. Compare source branch to target branch as if it'll be merged (just like HEAD diff on MR changes tab) if possible. 1. If not possible (e.g. conflict), revert to base comparison. 1. Track users using the "Changes" tab on the MR creation page.