Changing target branch after accepting merge request leads to incorrect information

Summary

We need the ability to reopen a merge request. In this case, we accepted a merge request into particular branch. When we changed the target branch of the merge request, it says that it's been merged, even though it's not in the target branch.

This is on Gitlab 8.14 EE.

Steps to reproduce

  1. Create feature_branch.
  2. Add simple commit to feature_branch.
  3. Create target_branch_1 off head commit of master
  4. Create target_branch_2 off head commit of master
  5. Create merge request to merge feature_branch into target_branch_1
  6. Accept merge request into target_branch_1
  7. Edit merge request to change target branch to target_branch_2
  8. Merge request now says it's been merged into target_branch_2
  9. Run git log on target_branch_2. Commits from feature_branch are not on target_branch_2

Expected behavior

Merge request status should change to open and show that it's not been merged into the target branch

Actual behavior

Merge request status says it's been merged into the target branch, even though it hasn't been.

Edited by 🤖 GitLab Bot 🤖