title: __git_ps1 not found when su username with Bash
body: <p>My current user, firstuser has a default shell of <code>/bin/sh</code></p>
  
  <p>My <code>.profile</code> is one line:</p>
  
  <pre><code>[ -f $HOME/.bash_profile ] &amp;&amp; . $HOME/.bash_profile
  </code></pre>
  
  <p>My <code>.bash_profile</code> is one line:</p>
  
  <pre><code>[ -f $HOME/.bashrc ] &amp;&amp; . $HOME/.bashrc
  </code></pre>
  
  <p>My <code>.bashrc</code> has the following code:</p>
  
  <pre><code>[ -f /usr/local/etc/bash_completion ] &amp;&amp; . /usr/local/etc/bash_completion
  export PS1='$(__git_ps1) \$  '
  </code></pre>
  
  <p>Here's the issue:</p>
  
  <pre><code>$  su seconduser
  Password:
  bash: __git_ps1: command not found
  $ 
  </code></pre>
  
  <p>Note:<br>
  seconduser has a shell of <code>/bin/bash</code></p>
  
  <p>What I want is all my customizations from firstuser to be carried into the shell of seconduser.</p>