Issue Summary

Changing the source branch in the "Create PR" page does not always update the PR description

Steps to Reproduce

1. In a repository that has more than two branches, go to Pull requests > Create pull request. If the preselected branch has more than one commit, the PR description gets populated with the messages of these commits.
2. Change the source branch of the PR. The PR description will get updated with the commit messages of the new source branch,
3. Change the source branch a second time.

Expected Results

The PR description gets updated with the commit messages of the new source branch.

Actual Results

The PR description doesn't get updated when the source branch is changed for a second (or third, fourth, etc.) time.

Workaround

• Go to the Branches page.
• Select the branch that will be the source branch for your pull request.
• Choose the destination branch from the drop-down menu or leave the default selection.
• Click on the "Create pull request" button.
• The selected branches will appear on the PR creation page.
• The description will be auto-filled based on your branch selections from the previous step