svn import fails when branch is created by a move

[David Allouche]

It looks like when a branch is created by a move (copy+delete) the initial imported revision is empty, which causes a failure on the first revision that tries to modify a pre-existing file.

In the case of the katapult import (svn://anonsvn.kde.org/home/kde/trunk/extragear/utils/katapult), the branch is created at revision 521764 by moving from /trunk/playground/utils/katapult:521763. The initial revision of the bzr import is an empty tree.