title: What does the git index contain EXACTLY?
body: <p>What does the Git index exactly contain, and what command can I use to view the content of the index?</p>
  <hr />
  <p>Thanks for all your answers. I know that the index acts as a staging area, and what is committed is in the index rather than the working tree. I am just curious about what an index object consists of. I guess it might be a list of filename/directory names, SHA-1 pairs, a kind of virtual tree maybe?</p>
  <p>Is there, in Git terminology, any <em>plumbing</em> command that I can use to list the contents of the index?</p>