Reindex commit branches when a branch is (forcefully) renamed or deleted (BB-8026)

For example, https://bitbucket.org/atlassian/jira/commits/42afd709b571230cbe9d60fa3a090ac8f840c191?at=atlassian_jira_6_0_OD_10_release_branch – the commit is present on the "atlassian_jira_6_0_OD_10_release_branch" branch, but the branch shows up as either emtpy or "OD10". This is because before being pushed to the release branch, it had been erroneously pushed to a new branched called "OD10". That branch was deleted shortly afterward, but not before bitbucket had a chance to index and cache it.