git diff --check always shows line 1 for blank at EOF for new files

Hi,

there seems to be a glitch in git diff --check for new files: If a new 
file has trailing empty lines, then the error message always refers to 
line 1. This happens with git 1.7.3.1.

Here is a simple test case:
   git init test
   cd test
   printf 'a\nb\nc\n\n' > file
   git add -AN
   git diff --check

The last command will show "file:1: new blank line at EOF.".

It works fine, if the diff is not against /dev/null, e.g.:
   git init test
   cd test
   printf 'a\nb\nc\n' > file
   git add -A
   echo >> file
   git diff --check

This correctly shows "file:4: new blank line at EOF.".