bzr push -r $revspec ../foo creates branch with working tree from tip, not that of $revspec

Explaining by example:

mwh@chinstrap:~$ bzr init-repo --rich-root-pack subvertpy
Shared repository with trees (format: rich-root-pack)
Location:
  shared repository: subvertpy
mwh@chinstrap:~$ cd subvertpy
mwh@chinstrap:~/subvertpy$ bzr get lp:subvertpy trunk
Branched 2143 revision(s).
mwh@chinstrap:~/subvertpy$ cd trunk/
mwh@chinstrap:~/subvertpy/trunk$ bzr push -r tag:subvertpy-0.7.0 ../subvertpy-0.7.0
Created new branch.
mwh@chinstrap:~/subvertpy/trunk$ cd ../subvertpy-0.7.0/
mwh@chinstrap:~/subvertpy/subvertpy-0.7.0$ bzr st
modified:
  NEWS
  setup.py
  subvertpy/__init__.py