How to squash commits

squash.sh

git remote add upstream git://github.com/callemall/material-ui.git # (or url of the repo you want to contribute)
git fetch upstream
git rebase -i HEAD~N # N is the number of commits you want to squash
# Let first commit to pick and pass the others to squash
# pick 1fc6c95 do something
# squash 6b2481b do something else
# squash dd1475d changed some things
# squash c619268 fixing typos
git config --global push.default simple
git push -f origin