With project administrator rights, the following actions are available for external repositories:

If the background synchronization is enabled, it periodically updates the repository. These background processes can be triggered by opening the options on the Repository Details view, and by bulk on the Repository Tracker table view. The update processes only fetch changes that are new to the repository, while the full synchronizations remove all items and re-synchronize the whole repository. The dangling commit cleanup removes the remaining commits after branch deletion. The cleanup job removes all the related items from the repository (commits, branches, tags), and disables the repository preventing further synchronization.