Here is detail of the error :

Counting objects: 8, done. Delta compression using 2 threads. Compressing objects: 100% (4/4), done. Writing objects: 100% (5/5), 1.37 KiB, done. Total 5 (delta 2), reused 0 (delta 0) error: insufficient permission for adding an object to repository database ./objects  fatal: failed to write object error: unpack-objects exited with error code 128 error: unpack failed: unpack-objects abnormal exit To git@github.com:bixo/bixo.git  ! [remote rejected] master -> master (n/a (unpacker error)) error: failed to push some refs to 'git@github.com:bixo/bixo.git'

Here is the solution: 

ssh me@myserver cd repository.git  sudo chmod -R g+ws * sudo chgrp -R mygroup *  git config core.sharedRepository true