Open the git log:
chris@dev:~/web$ git log

commit d3333478c9d1399ddc913e9cad726a10312971b6
Author: Chris Newland <chris@xyz.com>
Date:   Fri Sep 28 09:52:31 2012 +0000
User: cache db results in ramdisk
Change-Id: I73dfe6s7abe6abde6abd65ebc70bf3aebbc6cf89

commit c82f969ea9f1b5b1f02022d04dd9ed92c31340c7
Author: Chris Newland <chris@xyz.com>
Date:   Thu Sep 27 17:38:23 2012 +0000
User: eliminate redundant repaints
Change-Id: I7895bd15604a7a5b5d3f35ebc70bf3aebbc6cf89

commit 7e18cb6b86f3fe30da61a8b7a18fbec3ad20fd80
Author: Chris Newland <chris@xyz.com>
Date:   Thu Sep 27 17:00:01 2012 +0000
User: code refactor chart match
Change-Id: If7a8a3e4d5a5ed68490e8576eb8e701f2fdc6eee
To roll back the code, use git reset to the commit id before the change you want to unstage. So to unstage the last (top) commit, reset to the middle commit id:
git reset c82f969ea9f1b5b1f02022d04dd9ed92c31340c7