Issue Summary

When merging a pull request with a source branch that is the target branch of other pull requests, you are given the option to retarget the other pull requests. This option can sometimes fail to perform the retargeting and does not provide feedback when it fails.

Steps to Reproduce

1. Create 2 pull requests.
   1. The second pull request's destination branch should be the same as the source branch of the first pull request.
2. On the second pull request, add an inactive user as a reviewer
3. Click the Merge button on the first pull request
4. Make sure the box that says "Close source branch and retarget..." is checked
5. Click Merge

Expected Results

The second pull request's target branch should change to be the same as the first pull request's target. Failing that, some feedback should be provided for why retargeting didn't take place.

Actual Results

The second pull request's destination branch remains the now-deleted branch. No feedback is provided.

Workaround

The only currently known condition where this happens is when inactive users are reviewers on the pull request that is to be retargeted. Remove inactive users from the reviewers list prior to attempting to retarget.

If automatic retargeting fails, pull requests may be manually retargeted via the "Edit" page on the pull request view.