Feature request: Show merge SHA in MR widget after merging

It is often helpful to be able to quickly see the commit SHA of a merge that was made by a successful merge request.

1. You could click on it to see the pipeline that was run post-merge.
2. Release managers can use it to easily find the SHA they need to pick a merge into a stable branch.
3. If someone wants to manually revert a MR (i.e. not through the buttons in the MR widget), they can use the SHA string to find the diff.

In the case of a normal merge, this SHA should be the merge commit. If it was a rebase + fast-forward merge, it should be the SHA of the last commit. If it was a rebase + squash merge, it should be the SHA of the squashed commit applied to the target branch.

We could place it here:

(optionally with the type of merge indicated)

mentioned in issue gitlab-foss#33095 (closed)

related: https://gitlab.com/gitlab-org/gitlab-ce/issues/30224

few questions:

• is it confusing having a commit SHA that links to a pipeline? (rather than to the commit page)
• should we have copy button next to the hash? I think that's pretty common when we have SHAs

It would link to the commit page. It just so happens the commit page contains a pipeline on it (both a mini pipeline graph in the commit widget, and a tab to view associated pipelines). That's all I was inferring.

Yes, a copy button would be ideal.

Good idea! We already store the merge_commit_sha on the model, which should do what you want!

This seems pretty good as is :)

added to meta issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/33095

@victorwu can this be scheduled? This issue was mentioned in the description of https://gitlab.com/gitlab-org/gitlab-ce/issues/33095

changed milestone to %10.2

added Discussion in GitLab FOSS label

changed milestone to %Next 2-3 months in gitlab-foss

moved from gitlab-foss#34540 (moved)