Poor person's git squash

git-squash.sh

# start in a custom branch
git checkout <custom branch>

# make sure you have latest master pulled in
git pull origin master

# then diff out the difference between your branch and master
git diff origin/master > my.diff

# then delete your local branch
git checkout master
git branch -D <custom branch>

# recreate the branch
git branch <custom branch>
git checkout <custom branch>

# now apply the diff and add as a single commit
git apply my.diff
git commit -a -m "all changes in one clean commit"

# force push now which will overwrite remote branch with new branch with a single commit
git push -f

# start in a custom branch
git checkout
# make sure you have latest master pulled in
git pull origin master

Ah, interesting:

git pull origin master

should be done from within <custom branch>?

That's probably where my problems with the Studio Classic PRs (and the latest changes from master not showing) originated from.
I did do a pull, but from within master, not <custom branch>.