github squash once commits in PR

Question

Once a PR has been created, and commits are added slowly, can they later be squashed? I have created a PR, added a bunch of commits, and before I send for review want to squash so that the PR is clean.

I know this can be done by doing something like

git rebase -i HEAD~n (where n is number of commits)
// change last (n-1) picks to squash
// save and quit
// give new commit name

but these steps dont work once the PR is created

Answer 1

The changes are already made in the commit history so this isn't possible once you open a PR.

You have two options:

1. Close the PR, squash commits and open another PR
2. Squash the commits upon merging