recognize the new packed-ref header format
recognize the new packed-ref header format

as long as line contains "peeled", accept it
fixes the PackingType of packed-Refs not understood:
# pack-refs with: peeled fully-peeled sorted
problem

gitpython-developers/GitPython,gitpython-developers/GitPython,gitpython-developers/gitpython,gitpython-developers/gitpython