In my case, I had a feature branch that had a large file introduced. I'll call it feature-branch-1 (originally branched from master). I was unable to push this branch up to GitHub due to the large file in the history even though it had been deleted.

1. In feature-branch-1, I deleted the large file & also added it to gitignore, then committed locally.
2. Created a new branch from master called feature-branch-2
3. Merged feature-branch-1 INTO feature-branch-2 with the squash commits feature enabled
4. I was then able to successfully push feature-branch-2 up to GitHub

This was a very simple solution in my case where the large file was introduced in a feature branch that hadn't yet been merged into the primary master branch.