### Please describe the problem.
As per [this note](https://git-annex.branchable.com/todo/sharedRepository_mode_not_supported_by_git-annex/), `sharedRepository=world` should be supported. However, it does not seem to work with git-annex 5.20150508. When copying files to the public remote, annexed objects’ permission are subject to the remote user’s umask. If it is 077, they will not be world-readable.


### What steps will reproduce the problem?

[[!format sh """
# Remotely
git init --shared=world public
cd public
git config receive.denyCurrentBranch updateInstead
git annex init
"""]]

[[!format sh """
# Locally
git init local
cd local
git annex init
git remote add public $URL:public
echo abc > file
git annex add file
git commit -m init
git annex copy --to public file
git annex sync
# If remote user has umask 077, remote object winds up readable only by him
"""]]


### What version of git-annex are you using? On what operating system?
git-annex 5.20150508
Linux 4.0.4
