<!--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=434070) </details> <!--IssueSummary end--> <!--- Please read this! Before opening a new issue, make sure to search for keywords in the issues filtered by the "regression" or "type::bug" label: - https://gitlab.com/gitlab-org/gitlab/issues?label_name%5B%5D=regression - https://gitlab.com/gitlab-org/gitlab/issues?label_name%5B%5D=type::bug and verify the issue you're about to submit isn't a duplicate. ---> ### Problem Summary In https://gitlab.com/gitlab-org/gitlab/-/issues/428197 we changed `MergeRequest#should_be_rebased?` to be `false` when fast-forward merge trains are enabled, since fast-forward merge trains can automatically rebased. Users are no longer presented with a `rebase` button before `Merge immediately` action. This makes it so that `Merge immediately` will fail unless the user rebases, but there is no call to action to do so. See the users note: https://gitlab.com/gitlab-org/gitlab/-/issues/428197#note_1679362367 We then later hid the merge immediately button if the branch is behind which isn't ideal becuase it's not obvious why it's not there or how to get it back. But it will lead to less failures. https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138866 We need a manual or automatic way through the UI for the user to rebase prior to merging immediately so that we can unhide the merge immediately button when the mr source branch is ahead of the target branch. ### Steps to reproduce <!-- Describe how one can reproduce the issue - this is very important. Please use an ordered list. --> ### Example Project <!-- If possible, please create an example project here on GitLab.com that exhibits the problematic behavior, and link to it here in the bug report. If you are using an older version of GitLab, this will also determine whether the bug is fixed in a more recent version. --> ### What is the current *bug* behavior? <!-- Describe what actually happens. --> ### What is the expected *correct* behavior? <!-- Describe what you should see instead. --> ### Relevant logs and/or screenshots <!-- Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's tough to read otherwise. --> ### Output of checks <!-- If you are reporting a bug on GitLab.com, uncomment below --> <!-- This bug happens on GitLab.com --> <!-- /label ~"reproduced on GitLab.com" --> #### Results of GitLab environment info <!-- Input any relevant GitLab environment information if needed. --> <details> <summary>Expand for output related to GitLab environment info</summary> <pre> (For installations with omnibus-gitlab package run and paste the output of: `sudo gitlab-rake gitlab:env:info`) (For installations from source run and paste the output of: `sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`) </pre> </details> #### Results of GitLab application Check <!-- Input any relevant GitLab application check information if needed. --> <details> <summary>Expand for output related to the GitLab application check</summary> <pre> (For installations with omnibus-gitlab package run and paste the output of: `sudo gitlab-rake gitlab:check SANITIZE=true`) (For installations from source run and paste the output of: `sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true`) (we will only investigate if the tests are passing) </pre> </details> ### Proposal This MR is **blocked** by https://gitlab.com/gitlab-org/gitlab/-/issues/895 / https://gitlab.com/gitlab-org/gitlab/-/issues/444978. But when they are done, test whether it works with merge trains out of the box. The merging itself will almost certainly work, but there might be some checks on the backend and frontend that need to be tweaked to make the merge immediately button show again. ### Workarounds - When `Merge immediately` fails: Rebase the merge request, either using the `/rebase` quick action or locally - For `Rebase without pipeline`: Rebase locally and use the [`skip.ci` push option](https://docs.gitlab.com/ee/user/project/push_options.html#push-options-for-gitlab-cicd)