"cvs checkout: move away foo; it is in the way"

[kynn]

OK, here's an interaction that illustrates yet another bizarre (to me)
CVS conundrum (summary: I import some files, create a branch, modify
one file on this branch, commit it, delete the CVS directory, and
reimport):

  % export CVSROOT=/home/jones/cvs_test
  % rm -rf $CVSROOT
  % cvs init
  % mkdir Foo
  % cd Foo
  % touch foo
  % cvs im -m '' Foo vendor_1 v1
  N Foo/foo

  No conflicts created by this import

  % cvs co -d . Foo
  cvs checkout: Updating .
  U foo
  % cvs ta -b branch_1
  cvs tag: Tagging .
  T foo
  % cvs co -d . -r branch_1 Foo
  cvs checkout: Updating .
  % date
  % cvs ci -m '' foo
  Checking in foo;
  /home/jones/cvs_test/Foo/foo,v  <--  foo
  new revision: 1.1.1.1.2.1; previous revision: 1.1.1.1
  done
  % rm -rf CVS
  % cvs im -m '' Foo vendor_2 v2
  U Foo/foo

  No conflicts created by this import

  % cvs co -d . -r vendor_2 Foo
  cvs checkout: Updating .
  cvs checkout: move away foo; it is in the way
  C foo



Why am I getting the error message "cvs checkout: move away foo; it is
in the way"?  Can anyone make any sense of this?

Thanks!

kynn