$> git log -1
commit de1cea402d6f2856edc3f4df31382a7c42d4be62
Author: just me <[email protected]>
Date:   Wed May 2 22:00:50 2012 +0400

    EEEEE 9

[ ~/tmp/repo ]
$> git reset --hard HEAD~1
HEAD is now at f4fe738 EEEEE 8

[ ~/tmp/repo ]
$> git co de1cea402d6f2856edc3f4df31382a7c42d4be62
Note: checking out 'de1cea402d6f2856edc3f4df31382a7c42d4be62'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

HEAD is now at de1cea4... EEEEE 9

[ ~/tmp/repo ]
$> git log -1
commit de1cea402d6f2856edc3f4df31382a7c42d4be62
Author: just me <[email protected]>
Date:   Wed May 2 22:00:50 2012 +0400

    EEEEE 9