Don't allow changing target branch if the MR has been merged
Summary
When user edits MR after it has been merged, it's possible to change the target branch. After saving, the MR incorrectly shows the new edited target.
Steps to reproduce
- Edit on the right hand side.
- Change the branch and Save.
- The UI then says the changes were merged into the new branch.
Example Project
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What is the current bug behavior?
GUI allows target to be changed
What is the expected correct behavior?
GUI should not allow target to be changed post-merge
Relevant logs and/or screenshots
Output of checks
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Results of GitLab environment info
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Results of GitLab application Check
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(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true
)(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true
)(we will only investigate if the tests are passing)
Possible fixes
(If you can, link to the line of code that might be responsible for the problem)