Git: Combining the commits

To squash the last 3 commits into one:

git reset --soft HEAD~3
git commit -m "New message for the combined commit"

Pushing the squashed commit

If the commits have been pushed to the remote:

git push origin +name-of-branch

The plus sign forces the remote branch to accept your rewritten history, otherwise you will end up with divergent branches

If the commits have NOT yet been pushed to the remote:

git push origin name-of-branch