gistfile1.rb

users = search(:users, "repos:*")
shared_repos = search(:git_repos, "url:*")

users.each do |u|
  
  username = u['id']
  u["repos"].each do |target, repo|
      git "/home/#{username}/#{target}" do
        repository repo['repo']
        reference repo['revision']
        action :checkout
        user username
        ssh_wrapper "ssh -i /home/#{username}/.ssh/#{u['git_key']['name']}"
      end
  end

  shared_repos.each do |shared_repo|
    git "/home/#{username}/#{shared_repo['id']}" do
      repository shared_repo["url"]
      reference shared_repo["revision"]
      action :checkout
      user username
      ssh_wrapper "ssh -i /home/#{username}/.ssh/#{u['git_key']['name']}"
      only_if {File.exists?("/home/#{username}/.ssh/#{u['git_key']['name']}")}
    end
  end
end

gistfile2.txt

{ "id": "bert", 
"git_key": {
    "name": "git-key-rsa", 
    "public":"ssh-rsa ABCDEFG"
  },

gistfile3.txt

% knife data bag show git_repos test_lab
{
  "url": "[email protected]:test_lab.git",
  "id": "test_lab",
  "revision": "HEAD"
}