How to squash commits in git after they have been pushed?

Question

This gives a good explanation of squashing multiple commits:

http://git-scm.com/book/en/Git-Branching-Rebasing

but it does not work for commits that have already been pushed. How do I squash the most recent few commits both in my local and remote repos?

EDIT: When I do git rebase -i origin/master~4 master, keep the first one as pick, set the other three as squash, and then exit (via c-x c-c in emacs), I get:

$ git rebase -i origin/master~4 master
# Not currently on any branch.
nothing to commit (working directory clean)

Could not apply 2f40e2c... Revert "issue 4427: bpf device permission change option added"
$ git rebase -i origin/master~4 master
Interactive rebase already started

where 2f40 is the pick commit. And now none of the 4 commits appear in git log. I expected my editor to be restarted so that I could enter a commit message. What am I doing wrong?

Answer 1

Squash commits locally with

git rebase -i origin/master~4 master

and then force push with

git push origin +master

---

Difference between --force and +

From the documentation of git push:

Note that --force applies to all the refs that are pushed, hence using it with push.default set to matching or with multiple push destinations configured with remote.*.push may overwrite refs other than the current branch (including local refs that are strictly behind their remote counterpart). To force a push to only one branch, use a + in front of the refspec to push (e.g git push origin +master to force a push to the master branch).