# from http://stackoverflow.com/questions/5189560/squash-my-last-x-commits-together-using-git#5189600

# undo last X commits, and commit with a new message as one
git reset --soft HEAD~X
git commit -a -m "COMMIT MESSAGE"

# undo last X commits, and commit with old messages
git reset --soft HEAD~X 
git commit --edit -m"$(git log --format=%B --reverse HEAD..HEAD@{1})"

# the kosher way of doing previous example
git rebase -i <sha-of-last-commit-BEFORE-the-ones-you-are-after>
(this will open an editor window, where you have to manually change all the "pick" except the first one to "squash")

# undo the undo - if you change your mind
git reflog
> 54439b8 HEAD@{0}: reset: moving to HEAD~1
> 6fd9bfa HEAD@{1}: commit: YOUR COMMIT MESSAGE
> ...

git reset HEAD@{1} 
# or
git reset 6fd9bfa