Getting ready for an upstream pull request? You really need to turn it into a single commit for a clean request that will result in a fast-forward merge.

Switch to the upstream/master branch and make sure you are up to date.

git checkout master
git fetch upstream/master   
git merge master

Create a new feature/topic branch:

git checkout -b MyPullRequest
git merge MyMultiCommitBranch

Reset the branch to origin’s state.

git reset origin/MyPullRequest
git status

Note: Git now considers all changes as unstaged changes.

We can add these changes as one commit.

git add --all
git commit

You can push those changes to your remote repo and then issue that pull request to the upstream that you forked from.