Previously, GitHub's web UI did not allow deleting a branch that was associated with an open pull request. Now you can delete such a branch from the UI. However, doing so will close all open pull requests associated with the branch. Before the branch is deleted, you must confirm that the pull requests may be closed.
You can now require a successful deployment of a branch before its pull request can be merged. This is made possible by a new branch protection setting titled Require deployments to succeed before merging. To enable the setting, create a new branch protection rule for the target branch. Then, select the environments where deployments must succeed before a pull request can be merged, shown here:
This will allow you to ensure code is, for example, exercised in a staging or test environment before it's merged to your main branch.
Learn more about protected branches
Learn more about branch protection rules