Flip the last two commits in a branch using git-rebase, git-cherry-pick, git-update-ref, git-name-rev, and git-rev-parse. Interesting exercise using quite a bit of plumbing commands.

git-flip-last.sh

#!/bin/bash

branch=$(git name-rev --name-only HEAD)
git rebase --onto HEAD~2 HEAD~1 HEAD
git cherry-pick ORIG_HEAD~1
git update-ref refs/heads/$branch $(git rev-parse HEAD)
git checkout --quiet $branch

# Instead of creating an independant bash script with the code above, 
# consider simply creating a git alias using the command below.
#
# USAGE: git flip-last
git config --global alias.flip-last '!branch=$(git name-rev --name-only HEAD); git rebase --quiet --onto HEAD~2 HEAD~1 HEAD; git cherry-pick ORIG_HEAD~1; git update-ref refs/heads/$branch $(git rev-parse HEAD); git checkout --quiet $branch'

FYI, I have a concern about your gist : if something fails during either rebase or cherry-pick, you don't help the user and, worst, you reset his actual branch to the currently-in-failure sha1

I fixed those concerns in my fork here

• I use a temporary branch for my manipulations, resetting current branch only at the last step (only if everything went well before)
• I prefer to reset + cherry-pick 2 commit instead of rebase then cherry pick. In that case, I only have 1 potential failing step (the cherry pick) instead of 2 in your case (1 during rebase, the other during cherry pick)
• If something goes wrong, I warn the user and give him the command to execute to "resume" his work