User Problem

1. Based on Branch permission patterns, it's not possible to match negative patterns for the branch name.
2. For example, to allow users from a user group named Group A to be able to ONLY push to branch name group/a/**.

Suggested Solutions

1. To have the ability to match negative patterns for the branch name.

Current Workarounds

It's possible to use Scriptrunner for Bitbucket - Custom Pre-Receive Hooks to block changes from being pushed by checking the branch name and user triggered the hook.
Please take note that this is provided by a third-party app; Scriptrunner for Bitbucket.