$ git reflog expire --expire=1.minute refs/heads/master
$ git fsck --unreachable      # now I see those tarball blobs!
$ git prune                   # hasta la vista, baby
# git gc                      # cleanup and repack the repo

This example shows how to clean up git's reflogs entries in order save space (see http://www.newartisans.com/blog/2008/04/diving-into-git.html).

Clearing git reflog

git

Bash