Somewhat sped up git commit of modifications to unlocked files.

Avoid git reset here too, so I no longer need to care that it's much more
expensive than seems wise (but I asked the git list about that anyway).

It's not necessary to reset the staged file content from the index, as
the `git add` of the the symlink will replace it anyway.

`git commit` of unlocked files is still slow, since git still has to shove
their entire content into the index, only to have it be thrown away. So it's
still better to use `git annex add`

debian/changelog

@@ -5,6 +5,7 @@ git-annex (0.20110523) UNRELEASED; urgency=low
     `git reset`, and only running `git checkout` once, even when many files
     are being locked.
   * Fix locking of files with staged changes.
+  * Somewhat sped up `git commit` of modifications to unlocked files.
 
  -- Joey Hess <joeyh@debian.org>  Sat, 28 May 2011 22:29:37 -0400