'GET /api/repositories/get_installable_revisions
:param tsr_id: the encoded toolshed ID of the repository
Returns a list of lists of changesets, in the format [ [ 0, fbb391dc803c ], [ 1, 9d9ec4d9c03e ], [ 2, 9b5b20673b89 ], [ 3, e8c99ce51292 ] ].'

@web.expose_api_anonymous
def get_installable_revisions(self, trans, **kwd):

    tsr_id = kwd.get('tsr_id', None)
    if (tsr_id is not None):
        repository = repository_util.get_repository_in_tool_shed(self.app, tsr_id)
    else:
        error_message = 'Error    in    the    Tool    Shed    repositories    API    in    get_ordered_installable_revisions:    '
        error_message += 'missing    or    invalid    parameter    received.'
        log.debug(error_message)
        return []
    return repository.installable_revisions(self.app)
