How to force git to use specific permission settings when pushing via ssh

Question

I want to create a bare git repository in a shared directory so that multiple people (all of whom are in a particular UNIX group) can access it.

After creating the repository, all files and directories are owned by the creating user (creator) and owned by the group (group), but grant the same permissions to group and to everyone. After recursively giving full permissions to the owning group, and setting the setgid bit on directories (it's not the users' primary group, so it would not be used by default) the repository's filesystem structure looks like this:

TREE           PERMISSIONS OWNER  GROUP
repo           drwxrws--- creator group
| config       -rw-rw---- creator group
| description  -rw-rw---- creator group
| HEAD         -rw-rw---- creator group
| hooks        drwxrws--- creator group
| info         drwxrws--- creator group
| objects      drwxrws--- creator group
| refs         drwxrws--- creator group

When someone pushes and git creates a new file, the owner is always set to the user that pushed, and the permissions default to -rw-r--r-- (or drwxr-xr-x) so that other members of the group cannot overwrite those files later. For example, if user1 pushes a git object whose hash starts with 00, the directory structure now looks like this:

TREE              PERMISSIONS OWNER  GROUP
repo              drwxrws--- creator group
| config          -rw-rw---- creator group
| description     -rw-rw---- creator group
| HEAD            -rw-rw---- creator group
| hooks           drwxrws--- creator group
| info            drwxrws--- creator group
| objects         drwxrws--- creator group
| | 00            drwxr-sr-x user1   group
| | | (long name) -rw-r--r-- user1   group
| refs            drwxrws--- creator group

and now no other users can push objects that would be stored in repo/objects/00, because they don't have permissions to write to that directory.

How can I force git to make new files group-writable?

Answer 1

Check if the config core.sharedRepository could help in your target repo:

When group (or true), the repository is made shareable between several users in a group (making sure all the files and objects are group-writable).

But when it comes to ACL (Access Control Level) with git ssh, nothing is more easier or precise to put in place than gitolite (which is an authorization layer).