Shared Folder among Group Users
sudo groupadd project, create a group
/etc/group, list of the groups and users in each group
sudo usermod -a -G project user1, add user1 to group project
Create shared folder
sudo mkdir /home/project.git, create a shared folder
sudo chgrp -R project project.git, change it's group to be project
sudo chmod -R 2770 project.git, change mode to 770 and set up SGID
Reference