I found nothing in the documentation:
https://confluence.atlassian.com/bitbucket/fork-a-repo-compare-code-and-create-a-pull-request-mac-os-x-linux-271942986.html
https://confluence.atlassian.com/bitbucket/forking-a-repository-221449527.html
bitbucket cli seems not to be capable neiter:https://bitbucket.org/zhemao/bitbucket-cli
any advice / ideas?