I hear all that, but --bare is necessary in this case because git (by default) won't let you push to a non-bare filesystem branch:

    ~/temp/a:master  $ git push backup
    Enumerating objects: 3, done.
    Counting objects: 100% (3/3), done.
    Writing objects: 100% (3/3), 212 bytes | 212.00 KiB/s, done.
    Total 3 (delta 0), reused 0 (delta 0), pack-reused 0
    remote: error: refusing to update checked out branch: refs/heads/master
    remote: error: By default, updating the current branch in a non-bare repository
    remote: is denied, because it will make the index and work tree inconsistent
    remote: with what you pushed, and will require 'git reset --hard' to match
    remote: the work tree to HEAD.
    ...
    To ../b
    ! [remote rejected] master -> master (branch is currently checked out)
    error: failed to push some refs to '../b'