title: symfony bundle as git submodule
body: <p>I have two symfony2 projects with some bundles, theses project are under git management.</p>
  
  <p>Those 2 projects have 1 bundle in common, I want to make this bundle a submodule in order to merge the differences between project A and project B.</p>
  
  <p>I'v read this: <a href="https://stackoverflow.com/questions/11312333/splitting-directory-into-a-submodule">Splitting directory into a submodule</a> but i don't really understand how it works as the official git page (<a href="http://git-scm.com/book/en/Git-Tools-Submodules" rel="nofollow noreferrer">http://git-scm.com/book/en/Git-Tools-Submodules</a>) refer the command : <code>git submodule add</code></p>
  
  <p>So, how can I merge the two version of the commomBundle using submodules ?
  Will a commit to projectA or projectB allso commit the change for submodules ?</p>