add shared repository support

Created by: SaitoWu

Problem

The original bug report comes from here: https://groups.google.com/forum/?fromgroups=#!topic/gitlabhq/l1wSZmULJSo

Cause

This is a grack and gitolite cowork problem.

If u push over SSH, ur .git/objects 's permission look like this:

drwxrwx---  git:git

when u push over HTTP, ur .git/objects 's permission looks like this:

drwxr-xr-x gitlab:gitlab

so, git user didn't have group write permission on that object, and gitlab user will always have push permission.

Fix

To fix this problem, we need add a git config to each repo.

[core]
    sharedRepository = 0660

this will always give objects folder a drwxrws--- permission. like gitolites umask variable.

Gitolite support git config varible.

Our gitolite-client also support config variable, its easy to use:

repo.set_git_config("core.sharedRepository", "0660")

also we need edit .gitolite.rc file

GIT_CONFIG_KEYS             =>  '.*'

when we done what we do.

our new repo will have this in the config:

[core]
    repositoryformatversion = 0
    filemode = true
    bare = true
    sharedRepository = 0660 

And all things will work again.

TL;DR

merge this patch

edit .gitolite.rc file, GIT_CONFIG_KEYS => '.*'

will fix this problem.