Bitbucket DC should start supporting enhanced Git hashing (SHA-256) to increase the security of Git repositories.
In currently used Git hashing (SHA-1) known flaws have been discovered. SHA-1 is also vulnerable to the SHAttered attack which demonstrated a practical SHA-1 hash collision.

Please refer to:

• https://git-scm.com/docs/hash-function-transition
• Updating the Git protocol for SHA-256
• Git 2.42 released, SHA-256 repositories no longer an ‘experimental curiosity’
• Git version 2.42.0 release notes:

  Tone down the warning on SHA-256 repositories being an experimental curiosity. We do not have support for them to interoperate with traditional SHA-1 repositories, but at this point, we do not plan to make breaking changes to SHA-256 repositories and there is no longer need for such a strongly phrased warning.