bzr-svn follow a change of svn layout repository / missing history before restructurering

[Olivier R-D]

Hi,

I have used bzr against a svn server the last 2 year. the svn layout was
"root" this mean no trunk and branches
but yesterday the administrator create a layout with trunk and branches.
so everything moved under trunk.

so I dit a bzr branch xxx/trunk mytrunk
but writing a bzr log in mytrunk shows me only the last revisions after
restructuring.
for example :

bzr log agentmanager.py
------------------------------------------------------------
revno: 9
svn revno: 499 (on /trunk)
committer: ml
timestamp: Tue 2010-01-19 10:48:38 +0000
message:
   restructure.
olivier at utopie:~/svntesting/bzr/icehms$


then it is impossible to do any merge with my existing bzr branches
since I get
bzr merge ~/icemgr-branch/
bzr: ERROR: Branches have no common ancestor, and no merge base revision
was specified.

specifiying a a merge base like -r0.. bzr does not recognize any of the
files as identical and creates conflict everywhere ...

Does anyone has any idea of where the problem is ?
changing svn branch in bzr seems to work between trunk and one of the
new branches under branches/ but all history before the move from root
to trunk disapeared

thanks
Olivier