revision_trees with no parent

[Sandy Dunlop]

Hi,

In my code I call branch.repository.revision_trees([parentid,revid])
and then
delta = self.rev_tree.changes_from(self.parent_tree)
to get to get information about what's changed between two revisions.

This doesn't work if revid is the first revision (1st commit after the
branch has been inited). Can someone point me in the right direction
of what I should be doing to get the list of files that were added in
this revision?

Thanks,
Sandy