I'd rather not add a hard dependency on the `git` gem or other vcs gems like grit etc.. Perhaps we can look at how churn or turbulence do it, or with the git hash option do something like

```ruby
def select_git_hash
   require 'git'
   # do stuff
rescue LoadError
  STDERR.puts "Cannot select git hash; please install git gem"
  exit(1)
end
```