title: Git completion and PS1 not working: "__git_ps1: command not found" on "sudo -s" or "sudo su" on Ubuntu 12.04
body: <p>I installed git and git-flow completion adding these line to .bashrc of root and a normal_user on a Ubuntu 12.04 machine:</p>
  
  <pre><code>source /etc/git-completion.bash
  source /etc/git-flow-completion.bash
  GIT_PS1_SHOWUPSTREAM="verbose"
  GIT_PS1_SHOWDIRTYSTATE=true
  PS1='\[\033[32m\]\u@\h\[\033[00m\]:\[\033[34m\]\w\[\033[31m\]$(__git_ps1)\[\033[00m\]\$ '
  </code></pre>
  
  <p>When I log as root or normal_user git completion works. However if I use "sudo -s" or "sudo su" git completion is not working and I continually get "__git_ps1: command not found" each time I press return. 
  I tried to remove the "source" commands and use "apt-get install bash-completion" (bash-completion was already installed). So even without the 2 source I get the exact same behavior. </p>
  
  <p>Anybody knows what the problem is and how to make it work?</p>