How can I get content of a file from git index?

I have a file which has been already added to my local repository. I've modified it in the working tree, so git status shows me the file as modified. I would like to know what is the file content kept in the index before I stage the file.

I can think of two ways of doing that:

revert a patch generated by git diff, and apply it on the file in the working tree
use git checkout-index, point to a temporary file and read the content from there

Is there an easier way?

Solution

Use the : prefix to access objects in the current index (staged but not yet commited).

git show :file

See the gitrevisions manual for more information.