Make the `.git/safe` directory in `bin/setup`
Make the `.git/safe` directory in `bin/setup`

Assuming the binstubs for a project are in the local `bin/` directory,
we can add the directory to shell `$PATH` so that `rspec` can be invoked
without the `bin/` prefix:

    export PATH="./bin:$PATH"

Doing so on a system that other people have write access to (such as a
shared host) is a security risk:

sstephenson/rbenv#309

The `.git/safe` convention addresses the security problem:

https://twitter.com/tpope/status/165631968996900865

I used to do this manually before, as I have it in my `$PATH`
https://github.com/mehlah/dotfiles/blob/master/zshenv#L12-13

craftsmen/roll,craftsmen/roll,craftsmen/roll