Cannot add all commits to a merge-request
Summary
When having a merge request, we have the ability to add commits to this merge requests via the button "Add/remove previously merged commits". The list offered, allows one to remove (revert?) a commit from the existing set of the merge_target_branch. Adding a SHA1 of a different commit, appears to be working in terms of showing it in the list of commits, but the data never shows up. Also merging this commit, results in the actual diff from the listed SHA1 to now appear in the final result.
Steps to reproduce
Create a merge-request to merge code into master. From any other branch, find a commit to also be part of this merge request and copy its SHA1. On the initial merge request, go to the 'commits' tab and click the button 'Add previously merged commits' and paste the obtained SHA1 into the edit box. The commit now shows up in the list, select the checkbox and hit 'save'. The list of commits for the merge request had been expanded with the desired commit. But on the 'changes' tab, we do not see the changes. Also after merging, we do not see the changes.
Example Project
What is the current bug behavior?
The requested commit is not added to the branch of the merge request
What is the expected correct behavior?
The requested commit is added to the branch of the merge request
Output of checks
This bug happens on GitLab.com