Description of problem:

The guides mention the need to allow space when making backups or exporting repos, but I have not found a way to easily determine the on-disk size of a repo.

Such a tool would be appreciated. 

Additional info:

One way to do this would be to add a no-op option to the `hammer repository export` command which tells you the space that would be required.

Another way would be if the `hammer repo list` could provide that info. Whether the info is calculated on the fly or read from a value updated at repo sync time should not matter to the user.

As hammer commands get info from the API I will file this bug against the API component.


Thank you