string interpolation fail

in script.py:

        self.do_merge(from_repo_revision=self.from_branch,
                      to_repo_revision=self.to_branch,
                      merge_name='star-merge',
                      merge_method="do_star_merge",
                      line='merge %s %s' % (self.from_branch, self.to_branch))

The value of line here can contain % if the branch urls contain % (such as e.g. %7e) - this line is used in string formatting as the string to format later; either we should escape the urls appropriately, or we should (and this is probably better) pass the args to format further down, deferring any interpretation till the point of emission.