In epic https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/351 we discuss implementing changelog generation in GitLab, based on commit titles/messages. To make this easier for users, we want to extend GitLab to have the ability to edit commit messages on unprotected branches. :warning: For this epic we will focus exclusively on editing commit messages. Changing the wording/template for squashed commits and such is out of the scope of this epic. <details> <summary>Table of contents</summary> [[_TOC_]] </details> ## Status * Status: :hourglass_flowing_sand: in progress * DRI: @yorickpeterse ## The problem Editing commit messages can be difficult for those unfamiliar with `git rebase`, those new to Git, or those who simply don't want to rebase a bunch of merge request commits just to fix a few typos. GitLab doesn't provide any tools to help developers in these cases. The closest we have is the ability to edit merge commits when merging merge requests, but this leaves the original commits as-is. Using squash on merge in turn can lead to a loss of valuable history. If we want to use Git commit messages to generate changelogs, we need to tackle this problem so it becomes trivial to edit commit messages. ## Prior/related work * https://gitlab.com/groups/gitlab-org/-/epics/4941 * https://gitlab.com/gitlab-org/gitlab/-/issues/5316 * https://gitlab.com/gitlab-org/gitlab/-/issues/2551 * https://gitlab.com/gitlab-org/gitlab/-/issues/18142 * https://gitlab.com/groups/gitlab-org/-/epics/2894 The comments in https://gitlab.com/gitlab-org/gitlab/-/issues/2551 in particular show the interest in having this kind of functionality. ## Proposal When creating a merge request, the author of the merge request can edit the commit messages in one of two ways: 1. Using the merge request UI 1. By navigating to the individual commit, and editing its message there When members of the target project are allowed to commit to the merge request, they too can edit the commit messages. If the source branch is a protected branch, editing isn't possible. If the merge request is merged, project members can't edit the commit messages. When a commit is edited, a system note is created showing the diff of the commit message changes. The author of the system note will be the user that made the changes. If a commit is associated with a merge request, the note should be visible both when viewing the commit and when viewing the merge request. ## Success/exit criteria Users can edit commit messages through GitLab, removing the need to use `git rebase` for simple use cases. In addition, we aim for this to make our own developers more comfortable with the idea of using Git commits to drive our changelog generation process. ## Technical details Editing commit messages is to be done using `git rebase` or equivalent, not `git replace`, as `git replace` is not the right tool for this (see the comments in https://gitlab.com/gitlab-org/gitlab/-/issues/18142 regarding this). Gitaly will need to be extended to support some degree of commit rebasing. At the very least we should be able to give a commit SHA and a new commit message to use for that commit. We then need to extend the API to support this functionality, allowing us to use this in our frontend code. The frontend changes should ideally just use this API, instead of using a custom internal API. For this iteration we will focus on editing one commit at a time, instead of allowing for bulk edits. Bulk editing is something we may want to add in the future, but I think it's a step too far at this time. ## Future enhancements Enhancements we would make in the future include the ability to edit multiple commit messages in one API call, or to make it possible to submit review comments for commit messages. These enhancements are out of the scope of this epic.