please add an option to use a perment dir and not use an temp dir

[sergiomb2]

instead of pack and unpack cache-dir , let us have a dir with all prepared

[sergiomb2]

python3 svn2github.py --cache-dir /home/sergio/github/svn2github/virtualbox update sergiomb2/virtualbox

[sergiomb2]

I'm trying to keep svn2github of VirtuaBox , svn have 77970 commits and cache dir have 546M , pack and unpack 546 Megas takes a lot of time and CPU , I'd prefer have all in disk already unpacked