Combine 2 commits into one and update pull request

Finally, I was able to combine 2 commits into 1 commit and update the pull request. This will save me lots of time instead of creating a new pull request everytime and re-do work.

First time:

git clone <my-clone-of-upstream-repo>
cd <upstream-repo>
git remote add upstream <upstream-repo>
git config --global push.default simple

When starting a new pull request:

git checkout -b <new-branch>

Make changes, commit and send pull request. 

When combining n commits:

git fetch upstream
git merge-base new-branch master => This will generate a commit hash
git rebase --interactive <commit hash>

Your text editor will open with a file that lists all the commits in new-branch, and in front of each commit is the word "pick". For every line except the first, you want to replace the word "pick" with the word "squash" or "fixup". Save this file. 

git rebase upstream/master
git push -f

You're Done!

How to Rebase a Pull Request