Some cvs related fixes and enhancements

This patch series

    - fixes a small bug in the cvsimport testsuite
    - adds support for packed-refs to cvsserver
    - adds basic support cvs co -c to cvsserver

---
 git-cvsserver.perl              |   38 ++++++++++++++++++++++----------------
 t/t9400-git-cvsserver-server.sh |   25 +++++++++++++++++++++++++
 t/t9600-cvsimport.sh            |    1 +
 3 files changed, 48 insertions(+), 16 deletions(-)