In order to retrieve revrision from a Head, a query for all existinng branches is done

@Override
protected SCMRevision retrieve(SCMHead head, TaskListener listener) throws IOException, InterruptedException {
        final BitbucketApi bitbucket = buildBitbucketClient();
        List<? extends BitbucketBranch> branches = bitbucket.getBranches();

I think it is possible to obtain the revision from the API with a query for the specific Head.

This is causing heavy delays when starting builds, specially in Mercurial where branches cannot be deleted, they are just closed. Branches in API v2 is a paginated response, and in our case it is also hitting Bitbucket API rate limit.

With Bitbucket Cloud API v1 this was not a problem becasue closed branches where not included in the response for all branches.